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  • 1. BAKKER, ALBERT
    et al.
    GEJJI, SHRIDHAR
    LINDGREN, JAN
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    PROBST, MICHAEL M
    CONTACT ION-PAIR FORMATION AND ETHER OXYGEN COORDINATION IN THE POLYMER ELECTROLYTES M[N(CF3SO2)(2)](2)PEO(N) FOR M=MG, CA, SR AND BA1995In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 36, no 23, p. 4371-4378Article in journal (Refereed)
    Abstract [en]

    The polymer electrolytes M[N(CF3SO2)(2)](2)PEO(n) for M = Mg, Ca, Sr and Ba have been investigated using infra-red spectroscopy, differential scanning calorimetry and impedance spectroscopy. The effects of varying concentration (n = 6-40) and temperature (25-95 degrees C) on the contact ion pair formation and cation coordination have been studied. Contact ion pairs are only found for the most concentrated samples (n < 9). Ion pairs occur with two types of structures: one type is found far samples containing Mg2+ and the other for samples with Ca2+, Sr2+ and Ba2+. The conductivities of the samples are discussed in terms of radii and coordination numbers of the cations.

  • 2. GEJJI, SHRIDHAR P
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    LINDGREN, JAN
    ABINITIO VIBRATIONAL FREQUENCIES OF THE TRIFLATE ION, (CF3SO3)-1993In: J PHYS CHEM-US, ISSN 0022-3654, Vol. 97, no 15, p. 3712-3715Article in journal (Refereed)
    Abstract [en]

    The optimized geometry, harmonic vibrational frequencies and infrared intensities of the trifluoromethanesulfonate (triflate) ion, CF3SO3-, have been determined with ab initio self-consistent Hartree-Fock theory by using 3-21G* and 6-31G* Gaussian basis sets. Second-order Moller-Plesset perturbation calculations were also carried out with 6-31G* basis. A normal mode analysis shows that the vibrations assigned as symmetric and antisymmetric CF3 stretching involve other internal coordinates as well, viz., CF3 bending and CS stretching. The corresponding SO3 stretching modes, on the other hand, are almost entirely described with SO stretching coordinates. The assignments of the symmetric and antisymmetric SO3 and CF3 stretching vibrations from Moller-Plesset theory are seen to be different from those reported in the literature. Recent infrared spectroscopic experiments of the triflate ion coordinated to the zinc or lead ion in poly(ethylene oxide) complexes support the conclusions from second-order perturbation theory. The vibrational frequencies and infrared intensities show a strong dependence on basis set and electron correlation.

  • 3. GEJJI, SHRIDHAR P
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    LINDGREN, JAN
    AB-INITIO VIBRATIONAL FREQUENCIES OF THE TRIFLIC ACID MOLECULE1993In: J PHYS CHEM-US, ISSN 0022-3654, Vol. 97, no 27, p. 6986-6989Article in journal (Refereed)
    Abstract [en]

    The optimized geometry, harmonic vibrational frequencies, and infrared intensities of the trifluoromethanesulfonic (triflic) acid, CF3SO2OH, have been determined by ab initio self-consistent Hartree-Fock calculations and second-order Moller-Plesset perturbation theory with 6-31G** and lower basis sets. The optimized geometry of the triflic acid molecule is in good agreement with that reported from electron diffraction experiments. The overall symmetry for the molecule, however, is C1, and not C(s) as suggested from the experiments. The symmetric CF3 and SO2 stretching vibrational modes of the triflic acid are seen to be reversed compared to the assignment from the infrared spectra, reported earlier in the literature. The CF3 stretchings and the O=S=O bending normal modes include strong couplings of different internal coordinates. The vibrational frequencies and the infrared intensities are sensitive to the basis set choice as well as to electron correlation effects.

  • 4. GEJJI, SHRIDHAR P
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    LINDGREN, JAN
    STRUCTURE AND VIBRATIONAL FREQUENCIES OF THE MOLECULAR TRICHLOROMETHANESULFONIC ACID AND ITS ANION FROM AB-INITIO CALCULATIONS1994In: J PHYS CHEM-US, ISSN 0022-3654, Vol. 98, no 35, p. 8687-8692Article in journal (Refereed)
    Abstract [en]

    The equilibrium structure, vibrational frequencies, and the infrared intensities of the trichloromethanesulfonic acid molecule and its anion have been investigated using the ab initio self-consistent Hartree-Fock method and second-order Moller-Plesset perturbation theory with the 6-31G** and lower basis sets. A normal mode analysis shows that, unlike CCl3 stretchings, the SO3 stretching vibrations in the CCl3SO3- anion are pure normal modes comprised of S-O stretching coordinates only. The molecular point group for the trichloromethanesulfonic acid molecule is C-1 and not C-s. The vibrational frequencies and the infrared intensities are sensitive to the basis set choice as well as to the electron correlation effects.

  • 5. GEJJI, SHRIDHAR P
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    TEGENFELDT, JÖRGEN
    LINDGREN, JAN
    GEOMETRY AND VIBRATIONAL FREQUENCIES OF THE LITHIUM TRIFLATE ION-PAIR - AN AB-INITIO STUDY1993In: J PHYS CHEM-US, ISSN 0022-3654, Vol. 97, no 44, p. 11402-11407Article in journal (Refereed)
    Abstract [en]

    The optimized geometry, harmonic vibrational frequencies, and infrared absorption intensities of the lithium trifluoromethanesulfonate (triflate) ion pair, CF3SO3-Li have been investigated using the ab initio self-consistent Hartree-Fock and correlated second-order Moller-Plesset perturbation theory with the 6-31G* and lower basis sets. In the optimized structure the lithium cation is bound to two of the oxygens of the SO3 group forming a bidentate complex with C(s) symmetry. A local minimum with a monodentate structure was obtained in the HF/3-21G* calculations. The energy difference between the mono- and bidentate structures of the complex is predicted to be nearly 39 kJ mol-1 in this basis. A splitting of 230 and 158 cm-1 is obtained for the antisymmetric SO3 stretching for the bi- and monodentate coordination of the lithium cation with the free anion, respectively. The infrared spectrum of lithium triflate in poly(propylene oxide) shows a splitting of 43 cm-1. The strong interaction of the metal cation with the anion in the 1:1 complex thus overemphasizes the ''splitting behavior'' observed for lithium triflate dissolved in polymers. In the bidentate (MP2/6-31G*) complex the symmetric SO3 stretching shows a downshift of 38 cm-1, in contrast to an upshift of 47 cm-1 for the monodentate complex. The different signs of these frequency shifts have a purely geometric origin. The dependence of this frequency shift on the position of the Li+ ion is discussed.

  • 6.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    ABINITIO CALCULATIONS OF THE FUNDAMENTAL OH FREQUENCY OF BOUND OH- IONS1991In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 95, no 5, p. 3578-3588Article in journal (Refereed)
    Abstract [en]

    In contrast to the OH stretching frequencies of bound H2O molecules, which are always found at lower wave numbers compared to the free molecule, the experimentally determined frequency of the OH- ion can be either lower or higher than the free-ion value. Optimized geometries and fundamental stretching frequency of OH- have been calculated here by ab initio methods at the Hartree-Fock and second-order Moller-Plesset levels for a number of cation-OH-, HOH...OH-, cation-OH-.q-, and cation-OH-.OH2 complexes for Li+, Mg2+, and Al3+. The importance of electrostatic effects on the OH- frequency has been assessed by comparison with calculations of different point-charge and homogenous-field OH- systems. As long as the interaction is not dominated by electronic overlap, the frequency shift is found to be largely determined by electrostatic forces: with increasing field strength the OH- frequency rises to a maximum and then decreases. The OH- dipole moment and Mulliken charges vary monotonically with the field strength, whereas the equilibrium OH distance goes through a minimum and the bond electron density through a maximum. In strongly polarizing fields, such as in the optimized Al3+.OH- and Mg2+.OH-...OH2 systems, the OH- frequency falls below the free-ion value. Ar experimentally observed frequency downshift for an OH- ion in the condensed phase cannot be used as a criterion for the existence of H bonding. The OH- ion acts as an H-bond donor only when strongly polarized by a neighbor on its oxygen side.

  • 7.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    COMPUTER-SIMULATION AND ABINITIO CALCULATIONS OF SOME PROPERTIES OF LITHIUM FORMATE MONOHYDRATE1988In: Zeitschrift fur Kristallographie, ISSN 0044-2968, Vol. 182, no 1-4, p. 130-132Article in journal (Other academic)
  • 8.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    COORDINATION EFFECTS ON THE STRETCHING VIBRATION OF THE OH- ION1993In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 170, no 2, p. 177-184Article in journal (Refereed)
    Abstract [en]

    IR and Raman measurements on crystalline hydroxides reported in the literature have shown that both frequency upshifts and downshifts with respect to the free-ion frequency occur. Here the fundamental stretching vibrational frequency of a bound OH- ion in different point charge environments has been examined by ab initio calculations at the MP2 level. For a given geometry of a q+ . OH- . q- complex, the ab initio frequency is found to vary in a systematic way as the electric field is increased: the frequency increases, passes through a maximum and then decreases. Both the value of the maximum frequency and the field strength at which it occurs are highly dependent on the geometry of the complex. Only the field component parallel to the OH- axis is effective in changing the OH frequency. The arc-like shape of the frequency versus field correlation curves ''explains'' the large degree of non-additivity found for the environment-induced frequency shifts. H-bonds donated by the OH- ion may, or may not, lead to a frequency downshift, depending on the other neighbours present. It is also shown that a model which explicitly takes the field inhomogeneity into account (by a simple polynomial in E(parallel-to), (E(parallel-to))2, E(parallel-to)', (E(parallel-to)')2 and cross-terms, evaluated at two different ''probing sites'' in the ion), manages to represent the OH- frequency shift for an ''arbitrary'' point-charge environment.

  • 9.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    ELECTRIC-FIELD EFFECTS ON THE OH VIBRATIONAL FREQUENCY AND INFRARED-ABSORPTION INTENSITY FOR WATER1993In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 99, no 2, p. 861-868Article in journal (Refereed)
    Abstract [en]

    The variations of the anharmonic OH frequency and the infrared absorption intensity with field strength have been calculated for the uncoupled OH stretching vibration of a water molecule in a static, homogeneous electric field using ab initio methods at the MP4 level with a nearly saturated basis set. The OH frequency is found to be virtually independent of the field components perpendicular to the vibrating OH bond. For the parallel component, the frequency vs field curve is close to quadratic, with a maximum for a slightly negative (directed from H to 0) field strength. The external field perturbation, defined as V(ext)(E(parallel-to), r(OH)) = V(tot)(E(parallel-to), r(OH)) - V(free)(r(OH)), is found to be closely linear in r(OH), except when the field strength Ell is both large and negative. The linear external force constant is almost perfectly accounted for by the sum of two terms, -E(parallel-to).dmu(parallel-to)free/dr(OH) and -1/2.E(parallel-to).partial derivative mu(parallel-to)induced/partial derivative r(OH). These derivatives are quite insensitive to the choice of basis-set. The partial derivative mu(parallel-to)induced/partial derivative r(OH) derivative is approximately proportional to E(parallel-to), and gives rise to the arclike shape of the frequency vs field curve. The frequency maximum occurs where partial derivative mu(parallel-to)tot/partial derivative r(OH) almost-equal-to 0. It is the sign of dmu(parallel-to)free/dr(OH) which determines that the frequency maximum occurs at a negative field strength for water (but at a positive field strength for OH-, for example), i.e., that a frequency red-shift (blue-shift for OH-) occurs when the molecule is bound. The linear relationship between the infrared absorption intensity and frequency of the water OH vibration is derived.

  • 10.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    FROM CLUSTER TO CRYSTAL - ABINITIO CALCULATIONS OF THE OH- FREQUENCY IN LITHIUM HYDROXIDE MONOHYDRATE1992In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 159, no 1, p. 67-73Article in journal (Refereed)
    Abstract [en]

    The fundamental O-H stretching frequency of the OH- ion in crystalline LiOH.H2O has been calculated by ab initio methods at the MP2 level. The experimental and calculated wavenumbers are 3575 and 3602 cm-1, respectively. This frequency is shown to result from a delicate balance of several important interactions between the OH- ion and its surroundings: the two cations in the (Li+)2.OH- cluster produce an upshift of 75 cm-1 with respect to the isolated ion, while the whole nearest-neighbour cluster, (Li+)2(H2O)2.OH-.OH-, gives a frequency downshift of -570 cm-1. The crystal field outside the nearest-neighbour cluster produces an upshift of 610 cm-1. This behaviour conforms well with the frequency versus field correlation curves calculated for simple hydroxide point charge complexes.

  • 11.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    MANY-BODY EFFECTS IN TETRAHEDRAL WATER CLUSTERS1988In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 89, no 4, p. 2149-2159Article in journal (Refereed)
  • 12.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    O-H BONDS IN ELECTRIC-FIELDS - ELECTRON-DENSITIES AND VIBRATIONAL FREQUENCY-SHIFTS1995In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 233, no 4, p. 376-382Article in journal (Refereed)
    Abstract [en]

    The changes in the electron density distribution caused by varying the O-H bond length for HDO and OH- in uniform electric fields are investigated and related to the frequency shifts for the uncoupled O-H stretching vibration. Numerical integration of difference density maps, Delta rho=rho(r(OH)+Delta r(OH))-rho(r(OH)), reproduces the electronic contribution to theta mu(parallel to)(total)/theta r(OH), if the integration is carried out to a distance of approximate to 3.5 Angstrom from the O atom. The frequency shift Delta nu, is proportional to -E(parallel to) X[d mu(parallel to)(permanent)(r(OH))/dr(OH)]-1/2E(parallel to)[theta mu(parallel to)(induced)(E(parallel to), r(OH))/theta r(OH)] and electron density maps corresponding to the electronic parts of these terms are presented. Experimentally it has been found that the OH- ion shows a frequency upshift when bound in a moderately strong field, while water molecules show a downshift. The electron density maps show why d mu(parallel to)(permanent)(r(OH))/dr(OH) is positive for HDO and negative for OH-, resulting in a downshift for bound water an an upshift for bound OH-. For positive fields, theta mu(parallel to)(induced)/theta r(OH) is positive for both HDO and OH- and gives a downshift contribution.

  • 13.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    REDSHIFTS AND BLUESHIFTS OF OH VIBRATIONS1993In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 45, no 6, p. 747-758Article in journal (Refereed)
    Abstract [en]

    Ab initio calculations of potential energy, dipole moment, equilibrium OH distance, force constants, and anharmonic frequencies, and correlation between these quantities, are presented for a water molecule and an OH- ion in a uniform electric field of varying field strength. It is explained why a bound H2O molecule in nature always experiences a frequency downshift with respect to the free molecule, and a bound OH-1 ion, either a downshift or an upshift. The frequency-field variation is well accounted for by the expression DELTAnu(OH) is-proportional-to -E(parallel-to) . (dmu(parallel-to)free/dr(OH) + 1/2 . partial derivative mu(parallel-to)induced/partial derivative r(OH)). A frequency maximum occurs at the field strength where partial derivative mu(parallel-to)tot/partial derivative r(OH) is similar to 0. Two cases can be discerned: (1) the frequency maximum falls at a positive field strength when dmu(parallel-to)free/dr(OH) is positive (this is the situation for OH-), and (2) the maximum frequency falls at a negative field when dmu(parallel-to)free/dr(OH) is negative (this occurs for water). In general, for an OH bond in a bonding situation where the intermolecular interactions are dominated by electrostatic forces, the nonlinearity of the frequency shift with respect to an applied field is governed by how close to the frequency maximum one is, i.e., by both dmu(parallel-to)free/dr(OH) and partial derivative mu(parallel-to)induced/partial derivative r(OH). Correlation curves between the external linear force constant, k(ext), and r(OH,e) are closely linear over the whole field range studied here, whereas the frequency vs. r(OH,e) and force constants vs. r(OH,e) correlation curves form two approximately linear, parallel branches, corresponding to ''before'' and ''after'' the maximum in the frequency vs. field curves. Each branch of the nu vs. r(OH,e) curves has a slope of approximately -16,000 cm-1/angstrom.

  • 14.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    THE WATER FLIP BARRIER IN THE LI+HCOO-.H2O CRYSTAL FROM ABINITIO AND MOLECULAR MECHANICS CALCULATIONS1989In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 91, no 1, p. 368-375Article in journal (Refereed)
  • 15.
    HERMANSSON, KERSTI
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    KNUTS, SÖREN
    LINDGREN, JAN
    THE OH VIBRATIONAL-SPECTRUM OF LIQUID WATER FROM COMBINED ABINITIO AND MONTE-CARLO CALCULATIONS1991In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 95, no 10, p. 7486-7496Article in journal (Refereed)
    Abstract [en]

    The infrared vibrational OH stretching spectrum of isotopically isolated HDO molecules in liquid water has been calculated by ab initio methods at the MP2 level for a number of geometrical configurations taken from a Monte Carlo simulation. Each vibrating water molecule with its environment was described by a pentamer supermolecule, surrounded by a large number of point charges representing polarized water molecules. The anharmonic stretching potentials (MP2 force constants up to fifth order) for 40 uncoupled OH water vibrators were calculated. The average computed r(e) distance found for liquid water is 0.01 angstrom longer than the free-water value. The frequencies were obtained by solving the one-dimensional Schrodinger equation variationally for each OH potential curve. Using the squared dipole moment derivatives, which vary by a factor of 7 over the frequency band, the density-of-states histograms were converted to intensities. The resulting computed average frequency downshift is approximately 260 cm-1, compared to approximately 310 cm-1 (experimental), with a bandwidth in good agreement with experiment. The remaining discrepancy between theoretical and experimental frequency shifts is to a large part due to the charge transfer within the water clusters. This charge transfer gives rise to an electrostatic field which, at the site of the vibrating H atom, counteracts the downshift induced by the other environmental effects. The agreement between experiment and theory is very satisfactory when this charge transfer effect is corrected for or when point-charge embedded heptamer clusters are considered.

  • 16.
    HERMANSSON, KERSTI
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    LINDGREN, JAN
    PROBST, MICHAEL M
    NONADDITIVITY OF OH FREQUENCY-SHIFTS IN ION WATER-SYSTEMS1995In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 233, no 4, p. 371-375Article in journal (Refereed)
    Abstract [en]

    The intramolecular OH stretching frequency shift observed for water on formation of 'cation-water...H-bond acceptor' complexes is highly non additive. The uncoupled OH frequency shift has been calculated by ab initio methods for q(+)-OH2 and OH2...q(-) complexes of different geometries and for a series of Mg2+.(H2O)(n)...(H2O)(m) complexes, and we argue that the non-additivity (cooperativity) of the frequency shifts is largely a consequence of the parabolic shape of the frequency versus electric field curves.

  • 17.
    HERMANSSON, KERSTI
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    OJAMAE, LARS
    ON THE ROLE OF ELECTRIC-FIELDS FOR PROTON-TRANSFER IN WATER1995In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 77, p. 34-42Article in journal (Refereed)
    Abstract [en]

    The influence of uniform and non-uniform electric fields on one-dimensional proton transfer curves for (H2O)(2), H5O2+ and H3O2- has been examined using quantum-mechanical ab initio calculations. Both liquid-state and solid-state environments are discussed. For the charged complexes the transfer barrier is removed or greatly reduced by a field as small as 0.005 a.u. (2.5 X 10(7) V/cm). Local field fluctuations of this size are easily produced in condensed aqueous systems at room temperature. For the asymmetric single-well potential of an (H2O)(2) complex, a field ten times larger is needed to move the minimum from one side to the other across the O ... O bond. Such local fields can be achieved in ionic aqueous systems. The energy barrier for proton transfer in ice Ih has been computed using a periodic Hartree-Fock approach; the barrier for a fully concerted proton transfer is similar to 60 kJ/mol.

  • 18. KANSIKAS, JARNO
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    THE STRUCTURE OF LITHIUM FORMATE1989In: Acta Crystallographica Section C: Crystal Structure Communications, ISSN 0108-2701, E-ISSN 1600-5759, Vol. 45, p. 187-191Article in journal (Refereed)
  • 19. KNUTS, SÖREN
    et al.
    OJAMAE, LARS
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    AN AB-INITIO STUDY OF THE OH STRETCHING FREQUENCIES IN ICE-II, ICE-VIII, AND ICE-IX1993In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 99, no 4, p. 2917-2928Article in journal (Refereed)
    Abstract [en]

    Ab initio studies of the uncoupled, anharmonic OH and OD stretching frequency shifts in the three proton-ordered ice phases known, ice II, ice VIII, and ice IX, are presented. The ice structures are simulated by (H2O)5 supermolecules surrounded by point charges representing the correct crystal potentials. The calculations include electron correlation at the MP2 (DZP) level. For the eight different OH (OD) vibrators studied, the crystal environment leads to a downshift of the anharmonic OD frequency in the range 195-265 cm-1, in good agreement with experimental values (222-281 cm-1) when corrections are made for the limited supermolecular size (approximately - 45 cm-1), and, for ice VIII, also for the effects of the nonhydrogen bonded network (approximately + 75 cm- 1). Also the agreement between absolute experimental and theoretical OD frequencies is good when errors due to basis set limitation (approximately - 75 cm-1 ) are taken into account. The calculations suggest a reassignment of two of the experimental OD bands in ice II and all three experimental OD bands in ice IX. Calculations for charge-embedded (H2O)9 and (H2O)13 ice clusters show that at least a nonamer is needed to avoid boundary effects from the size of the supermolecule. Theoretical correlation curves between H-bond parameters-R (O ... 0), nu(OH), r(e)(OH), and infrared absorption intensity-are presented for the three ice phases and are compared to liquid water computations.

  • 20. LINDGREN, JAN
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    WOJCIK, MAREK J
    THEORETICAL SIMULATION AND EXPERIMENTAL-DETERMINATION OF OH AND OD STRETCHING BANDS OF ISOTOPICALLY DILUTED HDO MOLECULES IN AQUEOUS-ELECTROLYTE SOLUTIONS1993In: J PHYS CHEM-US, ISSN 0022-3654, Vol. 97, no 20, p. 5254-5259Article in journal (Refereed)
    Abstract [en]

    A combined theoretical and experimental study of the hydration of ions in aqueous electrolyte solutions is presented. Theoretical simulations of OH and OD stretching bands of isotopically diluted HDO molecules in a 0.44 m lithium formate solution have been performed. The positions of the atoms of the water molecules and the ions were taken from the trajectory file of a rigid-molecule room-temperature molecular dynamics simulation. V(r(OH)) potential energy functions were constructed as a sum of intra- and intermolecular energies and used in a variational calculation of the vibrational energy levels. Vibrational transition densities of states were calculated for HDO molecules in the first and second hydration shells of the ions. Infrared spectra of isotopically isolated HDO molecules in aqueous solutions of NaHCOO, LiClO4, NaClO4, Ca(ClO4)2, and Sr(ClO4)2 have been registered. The spectra were evaluated using an earlier developed double-difference method, where the number of ion-affected water molecules enters as a parameter in the analysis. In the present work, this number is obtained from the theoretical calculations, both for the Li+ and the HCOO- ion hydration. We find that OH/OD groups of water molecules in the second hydration shell of Li+, hydrogen-bonded to the first hydration shell, are affected by the ion. The earlier observed division of IR stretching frequencies for HDO molecules around cations into two distinct groups can now be explained by the presence or absence of such second-hydration-shell water molecules. For HDO molecules hydrogen-bonded to the HCOO- ions, the OH/OD frequency is lowered, compared to bulk water, for the OH/OD group involved in H-bonding to the ion, whereas the frequency is increased for the other OD/OH group, pointing away from the ion. The frequencies of HDO molecules surrounding the CH end of the formate ion are not influenced by the ion.

  • 21. OJAMAE, LARS
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    AB-INITIO STUDY OF COOPERATIVITY IN WATER CHAINS - BINDING-ENERGIES AND ANHARMONIC FREQUENCIES1994In: J PHYS CHEM-US, ISSN 0022-3654, Vol. 98, no 16, p. 4271-4282Article in journal (Refereed)
    Abstract [en]

    Many-body interaction energies and anharmonic OH stretching frequencies have been calculated for water in chain formations, in a ring structure, and in a tetrahedral arrangement. The calculations were of ab initio type, with the electron correlation energy included by Moller-Plesset perturbation correction to second order (MP2) and the basis-set superposition error corrected by the counterpoise procedure. The maximum chain length was seven water molecules, and the ring was five-membered. The molecules were H-bonded head-to-tail. The two- and many-body energies for the chains and ring are all of the same sign (negative), indicating strong cooperativity. The total nonadditivity contribution to the interaction energy is large, 16% for the longest chain and over 18% for the ring. The interaction energy of ah individual chain member with the rest of the chain shows even larger nonadditivity: over 25% for a molecule in the middle of the chain. This quantity should be of relevance for molecular dynamics simulations of liquid water. The OH stretching frequency downshift increases for all members of the chain with increasing chain length and is larger for molecules in the interior of the chain (-357 cm(-1) for the middle molecule in the 7-chain) than for terminal water molecules. The frequency converges only slowly for water molecules in the interior but faster for terminal water molecules. ''Frequency cooperativity'' was investigated by calculating many-body contributions in a manner analogous to the energy calculations. The chain and ring exhibit strong cooperativity. Infrared absorption intensities and charge transfer were investigated.

  • 22. OJAMAE, LARS
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    CRYSTAL ABINITIO INVESTIGATIONS OF ICE-II, ICE-VIII AND ICE-IX1994In: HYDROGEN BOND NETWORKS, 1994, p. 411-418Conference paper (Refereed)
  • 23. OJAMAE, LARS
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    THE OH STRETCHING FREQUENCY IN LICLO4-BULLET-3H2O(S) FROM ABINITIO AND MODEL POTENTIAL CALCULATIONS1992In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 161, no 1-2, p. 87-98Article in journal (Refereed)
    Abstract [en]

    The "in-crystal" frequency of the anharmonic and uncoupled OH stretching vibration of HDO molecules in LiClO4.3H2O(s) has been calculated by quantum-mechanical ab initio and model potential methods and compared with the experimental infrared frequency from isotope-isolated HDO molecules. The effects of the nearest neighbours as well as of the crystalline environment have been investigated by the two computational techniques. In both cases, the one-dimensional potential for an anharmonic OH oscillator was constructed from point-wise energy calculations and the Schrodinger equation for the protonic motion in this potential well was solved by a variational procedure. In the ab initio calculations, vibrational potentials were constructed from RHF and MP2 type calculations of point-charge embedded ClO4-.HDO and (Li+)2.(ClO4-)2.HDO clusters using DZP and TZP basis sets. For the LiClO4.3H2O(s) crystal, the ab initio OH frequency is in close quantitative agreement with experiment when electron correlation by MP2 and the crystal field are included: 3537 cm-1 (MP2(TZP)) versus the experimental value of 3556 cm-1. Inclusion of the crystal field is essential and can in this crystal be satisfactorily represented by Ewald field-consistent point charges outside the hydrogen-bonded ClO4-...HDO cluster. In the model potential calculations, analytical intermolecular pair potential functions from the literature were used in conjunction with an experimental intramolecular potential function for the OH stretching motion. The particular intermolecular model chosen here yields an absolute OH frequency 160 cm-1 below experiment. These calculations exemplify some of the difficulties encountered when employing analytical model potentials in vibrational studies.

  • 24. OJAMAE, LARS
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    WATER-MOLECULES IN DIFFERENT CRYSTAL SURROUNDINGS - VIBRATIONAL O-H FREQUENCIES FROM ABINITIO CALCULATIONS1992In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 96, no 12, p. 9035-9045Article in journal (Refereed)
    Abstract [en]

    Ab initio quantum-mechanical calculations of anharmonic frequencies for the water O-H vibrations have been performed for a series of crystalline hydrates. In each case, the potential-energy curve for the uncoupled water O-H stretch was derived at the Moller-Plesset MP2 level. Nearest neighbors of the water molecule were explicitly included in the supermolecule and the rest of the surroundings were mimicked by point charges to reproduce the crystal field out to infinity. The time-independent Schrodinger equation for the motion of the proton in this potential well was solved variationally and the frequency was obtained from the energy difference between the 0 and 1 eigenstates. Computed frequencies can be directly compared with existing infrared data for isotope-isolated water molecules in these hydrates. The compounds selected (LiClO4.3H2O, LiHCOO.H2O, LiOH.H2O) exhibit experimental O-H frequency shifts in a wide range, from - 150 down to - 930 cm-1. Good agreement is found between experimental and theoretical frequencies (experimental values in parentheses): 3596 (3556) for LiClO4.3H2O, 3129 (3112) and 3488 (3390) for LiHCOO.H2O, and 2817 (2775) cm-1 for LiOH.H2O. Correlation curves of typical H-bond parameters such as nu(O-H) vs R(H...O), r(e)(O-H) and nu(OH)/nu(OD) have been computed and compared with experiment. The vibrational intensities are also discussed.

  • 25. OJAMAE, LARS
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    DOVESI, ROBERTO
    ROETTI, CARLA
    SAUNDERS, VR
    MECHANICAL AND MOLECULAR-PROPERTIES OF ICE-VIII FROM CRYSTAL-ORBITAL AB-INITIO CALCULATIONS1994In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 100, no 3, p. 2128-2138Article in journal (Refereed)
    Abstract [en]

    The proton-ordered ice VIII structure has been investigated by ab initio periodic Hartree-Fock calculations in the pressure interval from 0 to 30 GPa using a 6-31G** basis set, The structure was optimized by energy-minimization at different volumes, and from the resulting energy vs volume relationship; the equation of state of ice VIII was derived; The variation of the structure,intramolecular geometry, Mulliken charges, electron density, Raman spectrum, and infrared stretching vibrations with varying pressure were investigated. The agreement with existing experimental data is generally good. Nearest-neighbor hydrogen-bonded O...O distances decrease from 2.88 to 2.57 Angstrom as the pressure is increased from 0 to 30 GPa. For the same: pressure range, the intramolecular OH bond increases from 0.951 to 0.955 Angstrom (giving a dr(OH)/dP value of 0.000 14 Angstrom/GPA), the Mulliken charge on H increases from +0.386 to +0.452, the calculated bulk modulus increases from similar to 25 to similar to 160 GPa), (corresponding experimental values ire similar to 25 at 2.4 GPa and similar to 135 at 30 GPa), and the electron density redistribution is considerably enhanced. The frequency downshift of the OH stretching vibration varies from -200 cm(-1) at 2.4 GPa to -500 cm(-1) at 20 GPa; the corresponding experimental values are -300 and -650 cm(-1). Electronic density-of-states diagrams are presented.

  • 26. OJAMAE, LARS
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    PISANI, CESARE
    CAUSA, MAURO
    ROETTI, CARLA
    STRUCTURAL, VIBRATIONAL AND ELECTRONIC-PROPERTIES OF A CRYSTALLINE HYDRATE FROM AB-INITIO PERIODIC HARTREE-FOCK CALCULATIONS1994In: Acta Crystallographica Section B: Structural Science, ISSN 0108-7681, E-ISSN 1600-5740, Vol. 50, p. 268-279Article in journal (Refereed)
    Abstract [en]

    The hydrate crystal lithium hydroxide monohydrate LiOH.H2O has been studied by ab initio periodic Hartree-Fock calculations. The influence of the crystalline environment on the local molecular properties (molecular geometry, atomic charges, electron density, molecular vibrations and deuterium quadrupole coupling constants) of the water molecule, the lithium and hydroxide ions has been calculated. A number of crystalline bulk properties are also presented, optimized crystalline structure, lattice energy and electronic band structure. The optimized cell parameters from calculations with a large basis set of triple-zeta quality differ by only 1-3% from the experimental neutron-determined cell, whereas the STO-3g basis set performs poorly (differences of 5-10%). With the triple-zeta basis also the atomic positions and intermolecular distances agree very well with the experiment. The lattice energy differs by approximately 8% from the experimental value, and by at most 3% when a density-functional electron correlation correction is applied. Large electron-density rearrangements occur in the water molecule and in the hydrogen bond and are in qualitative and quantitative agreement with experimental X-ray diffraction results. The quadrupole-coupling constants of the water and hydroxide deuterium atoms are found to be very sensitive to the O-H bond length and are in good agreement with experimental values when the calculation is based on the experimental structure. The anharmonic O-H stretching vibrations in the crystal are presented and found to be very close to results from calculations on molecular clusters. The electronic band and density-of-states spectra are discussed. Model calculations on a hydrogen fluoride chain were used to rationalize the results.

  • 27. OJAMAE, LARS
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    PROBST, MICHAEL
    THE OH STRETCHING FREQUENCY IN LIQUID WATER SIMULATIONS - THE CLASSICAL ERROR1992In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 191, no 5, p. 500-506Article in journal (Refereed)
    Abstract [en]

    OH stretching frequencies of HDO molecules in liquid water have been calculated by molecular dynamics simulation and compared to quantum-corrected OH stretching frequencies. In the MD simulation the MCY intermolecular water-water potential was used together with an experimental intramolecular free water potential. The frequencies calculated classically by Fourier transformation of the velocity autocorrelation function are found to be almost-equal-to 300 cm-1 too high compared with experiment. Quantum corrections show that the classical error contribution to this discrepancy is almost-equal-to 140 cm-1. To reach full agreement with experiment also the potential model needs to be improved. It is suggested that in constructing flexible water potentials the goal should not be set for an MD-derived OH frequency in absolute agreement with experiment (at 3400 cm-1) but instead some 200 cm-1 higher.

  • 28. OJAMAE, LARS
    et al.
    TEGENFELDT, JÖRGEN
    LINDGREN, JAN
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    SIMULATION OF BAND WIDTHS IN LIQUID WATER SPECTRA - THE BREAKDOWN OF THE FROZEN-FIELD APPROXIMATION1992In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 195, no 1, p. 97-103Article in journal (Refereed)
    Abstract [en]

    Band shapes of liquid water OH vibrational spectra oblained from molecular dynamics (MD) simulation and from a quantum-mechanical method are investigated. The so-called "frozen-field approximation" applied to the calculation of quantum-mechanical high-frequency vibrational spectra is critically examined. It is demonstrated that the band width of the OH stretching spectrum is seriously overestimated through the neglect of the dynamics of the environment in the frozen-field approximation. We show that the proper inclusion of the dynamics in this quantum-mechanical method leads not only to a correct absolute frequency for the model potential used, but also to the correct description of the band width. The basic steps in this method are: (1) an MD simulation yielding an ensemble of liquid water configurations, (2) a quantum-mechanical uncoupled local-mode calculation of the OH frequency for each molecule, using model potentials for the inter- and intra-molecular interactions, (3) inclusion of the influence from the dynamics of the surroundings by filtering out rapid frequency fluctuations. The remaining discrepancy between experimental and computed OH spectra is attributed to shortcomings in the potential model used.

  • 29. WOJCIK, MAREK J
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    LINDGREN, JAN
    OJAMAE, LARS
    THEORETICAL SIMULATION OF OH AND OD STRETCHING BANDS OF ISOTOPICALLY DILUTED HDO MOLECULES IN AQUEOUS-SOLUTION1993In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 171, no 1-2, p. 189-201Article in journal (Refereed)
    Abstract [en]

    Uncoupled OH and OD stretching bands of HDO molecules have been calculated for an ionic aqueous solution, based on the trajectories from a classical statistical-mechanical computer simulation and subsequent quantum-mechanical calculations of the vibrational energy levels. Each V(r(OH)) potential function has been constructed as a sum of intra- and intermolecular energies, where different intermolecular water-water potential functions from the literature (MCY, TIPS2, RWK2 and CF2) have been tested in conjunction with the experimentally derived HMS intramolecular potential. In this way, vibrational densities-of-states as well as infrared absorption bands have been calculated for HDO molecules in the bulk and in the ionic hydration shells (Li+, HCOO-). Calculated frequencies and band widths for the TIPS2 and MCY potentials are fairly close to experimental values. The calculated OH shift between the gas and liquid water phases is - 303 cm-1 with the TIPS2 potential, as compared to the experimental value of - 307 cm-1. The MCY potential gives - 260 cm-1, while RWK2 as well as the CF2 potentials give rise to a non-negligible number of spurious frequencies. Water molecules in the first hydration shell of Li+ exhibit only slightly lower stretching frequencies than bulk water. The frequencies of the OH and OD groups of HDO molecules bonded to the formate oxygen atoms are lower than in bulk water, while the frequency of the OH/OD group pointing away from the formate ion is higher compared to bulk water.

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