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Publications (10 of 234) Show all publications
Ivanov, S., Beran, P., Bush, A. A., Sarkar, T., Shafeie, S., Wang, D., . . . Mathieu, R. (2019). Cation ordering, ferrimagnetism and ferroelectric relaxor behavior in Pb(Fe1-xScx)(2/3)W1/3O3 solid solutions. European Physical Journal B: Condensed Matter Physics, 92(8), Article ID 163.
Open this publication in new window or tab >>Cation ordering, ferrimagnetism and ferroelectric relaxor behavior in Pb(Fe1-xScx)(2/3)W1/3O3 solid solutions
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2019 (English)In: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 92, no 8, article id 163Article in journal (Refereed) Published
Abstract [en]

Ceramic samples of the multiferroic perovskite Pb(Fe1-xScx)(2/3)W1/3O3 with 0 <= x <= 0.4 have been synthesized using a conventional solid-state reaction method, and investigated experimentally and theoretically using first-principle calculations. Rietveld analyses of joint synchrotron X-ray and neutron diffraction patterns show the formation of a pure crystalline phase with cubic (Fm3(_)m) structure with partial ordering in the B-sites. The replacement of Fe by Sc leads to the increase of the cation order between the B and B '' sites. As the non-magnetic Sc3+ ions replace the magnetic Fe3+ cations, the antiferromagnetic state of PbFe2/3W1/3O3 is turned into a ferrimagnetic state reflecting the different magnitude of the magnetic moments on the B ' and B '' sites. The materials remain ferroelectric relaxors with increasing Sc content. Results from experiments on annealed and quenched samples show that the cooling rate after high temperature annealing controls the degree of cationic order in Pb(Fe1-xScx)(2/3)W1/3O3 and possibly also in the undoped PbFe2/3W1/3O3.

Place, publisher, year, edition, pages
SPRINGER, 2019
Keywords
Solid State and Materials
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-392576 (URN)10.1140/epjb/e2019-100149-9 (DOI)000477626500002 ()
Funder
Swedish Research Council
Available from: 2019-09-09 Created: 2019-09-09 Last updated: 2019-09-09Bibliographically approved
Rahmani, N., Ghazi, M. E., Izadifard, M., Wang, D., Shabani, A. & Sanyal, B. (2019). Density functional study of structural, electronic and magnetic properties of new half-metallic ferromagnetic double perovskite Sr2MnVO6. Journal of Physics: Condensed Matter, 31(47), Article ID 475501.
Open this publication in new window or tab >>Density functional study of structural, electronic and magnetic properties of new half-metallic ferromagnetic double perovskite Sr2MnVO6
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2019 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 31, no 47, article id 475501Article in journal (Refereed) Published
Abstract [en]

In this paper, a new half-metallic (HM) double perovskite compound is predicted with the simultaneous presence of ferromagnetism and polar distortion. The structural, electronic and magnetic properties of Sr2MnVO6 (SMVO) are calculated by density functional theory (DFT) with both generalized gradient approximation (GGA) and GGA + U approaches, where U is the on-site Coulomb interaction parameter. Different orderings of B (B') cationic sites in A(2)BB'O-6 double perovskite structure are evaluated, including rocksalt, columnar and layered arrangements for cubic, monoclinic and tetragonal crystal structures. It is found that the most stable ordering is obtained when B and B' are placed in a layered type ordering for a tetragonal crystal structure with I4/m space group, which is confirmed by phonon calculations. The B-site ordering of the Mn3+ and V5+ ions in a layered configuration leads to ferromagnetically coupled magnetic moments of 4.17 mu(B) at Mn site and 0.23 mu(B) at V site. Finally, SMVO is found to be a half-metallic ferromagnetic (HM-FM) compound with a band gap of 0.65 eV in a spin down channel with off-centered displacement of V atoms in the octahedral cage (second order Jahn-Teller effect) which can cause ferroelectricity. Therefore, SMVO is predicted to be a polar HM material and a promising candidate for multiferroic property with potential application in spintronics.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
double perovskite Sr2MnVO6, multiferroics, half-metallic, density functional theory
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-393714 (URN)10.1088/1361-648X/ab35f7 (DOI)000482531700001 ()31349237 (PubMedID)
Funder
Swedish Research Council, 2016-05366Swedish Research Council, 2017-05447
Available from: 2019-09-30 Created: 2019-09-30 Last updated: 2019-09-30Bibliographically approved
Akansel, S., Kumar, A., Venugopal, V. A., Esteban-Puyuelo, R., Banerjee, R., Autieri, C., . . . Svedlindh, P. (2019). Enhanced Gilbert damping in Re-doped FeCo films: Combined experimental and theoretical study. Physical Review B, 99(17), Article ID 174408.
Open this publication in new window or tab >>Enhanced Gilbert damping in Re-doped FeCo films: Combined experimental and theoretical study
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 17, article id 174408Article in journal (Refereed) Published
Abstract [en]

The effects of rhenium doping in the range 0-10 at.% on the static and dynamic magnetic properties of Fe65Co35 thin films have been studied experimentally as well as with first-principles electronic structure calculations focusing on the change of the saturation magnetization (M-s) and the Gilbert damping parameter (alpha). Both experimental and theoretical results show that M-s decreases with increasing Re-doping level, while at the same time alpha increases. The experimental low temperature saturation magnetic induction exhibits a 29% decrease, from 2.31 to 1.64 T, in the investigated doping concentration range, which is more than predicted by the theoretical calculations. The room temperature value of the damping parameter obtained from ferromagnetic resonance measurements, correcting for extrinsic contributions to the damping, is for the undoped sample 2.1 x 10(-3), which is close to the theoretically calculated Gilbert damping parameter. With 10 at.% Re doping, the damping parameter increases to 7.8 x 10(-3), which is in good agreement with the theoretical value of 7.3 x 10(-3). The increase in damping parameter with Re doping is explained by the increase in the density of states at the Fermi level, mostly contributed by the spin-up channel of Re. Moreover, both experimental and theoretical values for the damping parameter weakly decrease with decreasing temperature.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-387290 (URN)10.1103/PhysRevB.99.174408 (DOI)000467722100005 ()
Funder
Knut and Alice Wallenberg Foundation, KAW 2012.0031Swedish Research Council, 2016-05366
Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-06-24Bibliographically approved
Brumboiu, I. E., Haldar, S., Lüder, J., Eriksson, O., Herper, H. C., Brena, B. & Sanyal, B. (2019). Ligand effects on the linear response Hubbard U: The case of transition metal phthalocyanines. Journal of Physical Chemistry A, 123(14), 3214-3222
Open this publication in new window or tab >>Ligand effects on the linear response Hubbard U: The case of transition metal phthalocyanines
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2019 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 123, no 14, p. 3214-3222Article in journal (Refereed) Published
Abstract [en]

It is established that density functional theory (DFT) + U is a better choice compared to DFT for describing the correlated electron metal center in organometallics. The value of the Hubbard U parameter may be determined from linear response, either by considering the response of the metal site alone or by additionally considering the response of other sites in the compound. We analyze here in detail the influence of ligand shells of increasing size on the U parameter calculated from the linear response for five transition metal phthalocyanines. We show that the calculated multiple-site U is larger than the single-site U by as much as 1 eV and the ligand atoms that are mainly responsible for this difference are the isoindole nitrogen atoms directly bonded to the central metal atom. This suggests that a different U value may be required for computations of chemisorbed molecules compared to physisorbed and gas-phase cases.

National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-300117 (URN)10.1021/acs.jpca.8b11940 (DOI)000464768100011 ()30892039 (PubMedID)
Funder
Swedish Research Council, 2014-3776Swedish Research Council, 2016-05366Swedish Research Council, 2017-05447Knut and Alice Wallenberg Foundation, KAW-2013.0020Swedish National Infrastructure for Computing (SNIC)
Available from: 2016-08-02 Created: 2016-08-02 Last updated: 2019-05-15Bibliographically approved
Wen, X., Liu, Y., Jadhav, A., Zhang, J., Borchardt, D., Shi, J., . . . Guo, J. (2019). Materials Compatibility in Rechargeable Aluminum Batteries: Chemical and Electrochemical Properties between Vanadium Pentoxide and Chloroaluminate Ionic Liquids. Chemistry of Materials, 31(18), 7238-7247
Open this publication in new window or tab >>Materials Compatibility in Rechargeable Aluminum Batteries: Chemical and Electrochemical Properties between Vanadium Pentoxide and Chloroaluminate Ionic Liquids
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2019 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 18, p. 7238-7247Article in journal (Refereed) Published
Abstract [en]

To demonstrate the importance of electrode/electrolyte stability in rechargeable aluminum (Al) batteries, we investigate the chemical compatibility between vanadium pentoxide (V2O5), a proposed positive electrode material for Al batteries, and the common chloroaluminate ionic liquid electrolytes. We reveal that V2O5 reacts with both the Lewis acidic (Al2Cl7-) and the Lewis neutral species (AlCl4-) within the electrolyte. The reaction products are identified using a combination of electrochemical analyses, Raman spectroscopy, liquid-state and solid-state nuclear magnetic resonance (NMR) spectroscopy, and density functional theory (DFT) calculations. The results establish that V2O5 chemically reacts with Al2Cl7- to form vanadium oxychloride (VOCl3) and amorphous aluminum oxide. V2O5 also chemically reacts with AlCl4- to produce dioxovanadium chloride (VO2Cl) and a new species of metavanadate anion coordinated with aluminum chloride (AlCl3VO3-). These products furthermore exhibit electrochemical redox activity between V5+ and V2+ oxidation states. Our results have significant implications when interpreting the electrochemical properties and mechanisms of rechargeable Al-V2O5 batteries.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-395841 (URN)10.1021/acs.chemmater.9b01556 (DOI)000487859200016 ()
Funder
Swedish Research Council, 2017-05447Swedish Research Council, 2016-05366Swedish National Infrastructure for Computing (SNIC), SNIC 2018/2-51
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25Bibliographically approved
Vovusha, H., Banerjee, D., Yadav, M. K., Perrozzi, F., Ottaviano, L., Sanyal, S. & Sanyal, B. (2018). Binding Characteristics of Anticancer Drug Doxorubicin with Two-Dimensional Graphene and Graphene Oxide: Insights from Density Functional Theory Calculations and Fluorescence Spectroscopy. The Journal of Physical Chemistry C, 122(36), 21031-21038
Open this publication in new window or tab >>Binding Characteristics of Anticancer Drug Doxorubicin with Two-Dimensional Graphene and Graphene Oxide: Insights from Density Functional Theory Calculations and Fluorescence Spectroscopy
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2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 36, p. 21031-21038Article in journal (Refereed) Published
Abstract [en]

There has been a perpetual interest in identifying suitable nano-carriers for drug delivery. In this regard, graphene-based two-dimensional materials have been proposed and demonstrated as drug carriers. In this paper, we have investigated the adsorption characteristics of a widely used anticancer drug, doxorubicin (DOX), on graphene (G) and graphene oxide (GO) by density functional theory calculations and fluorescence and X-ray photoelectron spectroscopies. From the calculated structural and electronic properties, we have concluded that G is a better binder of DOX compared to GO, which is also supported by our fluorescence measurements. The binding of DOX to G is mainly based on strong pi-pi stacking interactions. Consistent with this result, we also found that the sp(2) regions of GO interact with DOX stronger than the sp(3) regions attached with the functional groups; the binding is characterized by pi-pi and hydrogen-bonding interactions, respectively.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-366741 (URN)10.1021/acs.jpcc.8b04496 (DOI)000444920900049 ()
Funder
Swedish Research Council, 2016-05366Swedish Research Council, 20144423Swedish Research Council, 2017-05447Knut and Alice Wallenberg Foundation, KAW 2017.0055
Available from: 2018-12-10 Created: 2018-12-10 Last updated: 2019-05-17Bibliographically approved
Kou, R. H., Gao, J., Ren, Y., Sanyal, B., Bhandary, S., Heald, S. M., . . . Sun, C.-J. -. (2018). Charge transfer-tuned magnetism in Nd-substituted Gd5Si4. AIP Advances, 8(12), Article ID 125219.
Open this publication in new window or tab >>Charge transfer-tuned magnetism in Nd-substituted Gd5Si4
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2018 (English)In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 8, no 12, article id 125219Article in journal (Refereed) Published
Abstract [en]

We report a charge-transfer mechanism in tuning of magnetism of Nd-substituted Gd5-xNdxSi4 (x=1 and 2.5) compounds. The X-ray absorption near edge structure measurements demonstrated that Nd substitutions for Gd induce charge transfer of 5d electrons from Gd to Nd. The charge transfer weakens spin-orbital coupling of Gd but strengthens that of Nd. Consequently, the magnetization responses of the substituted compounds to low magnetic fields are increased while their saturation magnetization is reduced. Electronic structure calculations showed that the charge transfer stabilizes a ferromagnetic and a ferrimagnetic structure in the compounds with x = 1 and 2.5, respectively, but that it does not change the 5d-3p hybridization significantly. It is suggested that the charge transfer of 5d electrons may occur in other rare earth-substituted Gd5Si4 compounds allowing for tuning of their magnetism.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-374127 (URN)10.1063/1.5081457 (DOI)000454615100077 ()
Available from: 2019-01-18 Created: 2019-01-18 Last updated: 2019-01-18Bibliographically approved
Haldar, S., Bhandary, S., Vovusha, H. & Sanyal, B. (2018). Comparative study of electronic and magnetic properties of iron and cobalt phthalocyanine molecules physisorbed on two-dimensional MoS2 and graphene. Physical Review B, 98(8), Article ID 085440.
Open this publication in new window or tab >>Comparative study of electronic and magnetic properties of iron and cobalt phthalocyanine molecules physisorbed on two-dimensional MoS2 and graphene
2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 98, no 8, article id 085440Article in journal (Refereed) Published
Abstract [en]

In this paper, we have done a comparative theoretical study of electronic and magnetic properties of iron phthalocyanine (FePc) and cobalt phthalocyanine (CoPc) molecules physisorbed on a monolayer of MoS2 and graphene by density functional theory. Various types of physisorption sites have been considered for both surfaces. The lowest energy structure for both metal phthalocyanine (MPc) molecules physisorbed on MoS2 is a sulfur-top position, i.e., when the metal center of the molecule is on top of a sulfur atom. However, on graphene, the lowest energy structure for the FePc molecule is when a metal atom is on top of a bridge position. In contrast to this, the CoPc molecule prefers a carbon-top position. The adsorption of MPc molecules is stronger on the MoS(2 )surface than on graphene (similar to 2.5 eV higher physisorption energy). In these systems, spin dipole moments of the metal centers are antiparallel to the spin moments and hence a huge reduction of effective spin moment can be seen. The calculations of magnetic anisotropy energies using both variational and second-order perturbation approaches indicate no significant changes after physisorption. In case of the FePc and CoPc physisorption, respectively, an out-of-plane and an in-plane easy axis of magnetization can be observed. Our calculations indicate a reduction of MoS2 work function similar to 1 eV due to physisorption of MPc molecules while it does not change significantly in the case of graphene.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-364179 (URN)10.1103/PhysRevB.98.085440 (DOI)000443395600008 ()
Funder
Swedish Research Council, 2017-05447
Available from: 2018-11-01 Created: 2018-11-01 Last updated: 2018-11-01Bibliographically approved
Vovusha, H., Amorim, R. G., Scheicher, R. H. & Sanyal, B. (2018). Controlling the orientation of nucleobases by dipole moment interaction with graphene/h-BN interfaces. RSC Advances, 8(12), 6527-6531
Open this publication in new window or tab >>Controlling the orientation of nucleobases by dipole moment interaction with graphene/h-BN interfaces
2018 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 8, no 12, p. 6527-6531Article in journal (Refereed) Published
Abstract [en]

The interfaces in 2D hybrids of graphene and h-BN provide interesting possibilities of adsorbing and manipulating atomic and molecular entities. In this paper, with the aid of density functional theory, we demonstrate the adsorption characteristics of DNA nucleobases at different interfaces of 2D hybrid nanoflakes of graphene and h-BN. The interfaces provide stronger binding to the nucleobases in comparison to pure graphene and h-BN nanoflakes. It is also revealed that the individual dipole moments of the nucleobases and nanoflakes dictate the orientation of the nucleobases at the interfaces of the hybrid structures. The results of our study point towards a possible route to selectively control the orientation of individual molecules in biosensors.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-347655 (URN)10.1039/c7ra11664k (DOI)000425034000041 ()
Funder
Knut and Alice Wallenberg FoundationSwedish Research CouncilCarl Tryggers foundation
Available from: 2018-04-06 Created: 2018-04-06 Last updated: 2018-04-06Bibliographically approved
Samanta, S., Raghunathan, D., Mukherjee, S. & Sanyal, B. (2018). Dependence of homo-lumo gap of DNA base pair steps on twist angle: A density fuctional approach. Journal of biological systems, 26(1), 23-40
Open this publication in new window or tab >>Dependence of homo-lumo gap of DNA base pair steps on twist angle: A density fuctional approach
2018 (English)In: Journal of biological systems, ISSN 0218-3390, Vol. 26, no 1, p. 23-40Article in journal (Refereed) Published
Abstract [en]

Electronic structure calculations of all 10 unique base pair (bp) steps have been calculated to study the interaction energies of the bp steps, density of states (DOS), projected density of states (pDOS) using the density functional theory (DFT). Plane wave basis with ultrasoft pseudo-potential method has been used within the local density approximation (LDA) for the exchange correlation functional. Electron densities of the bp steps corresponding to HOMO and LUMO level have been calculated to understand the difference in stacking energies of the bp steps. The variation of HOMO-LUMO gap (g) of all possible bp steps on twist angle has been studied. We have observed that out of the 10 bp steps, 4 purine-purine bp steps (d(AA), d(GG), d(AG) and d(GA)), show significant variation of g on twist angle. The observed variation on twist angle of d(AA) bp step has been explained by the calculated DOS and electron densities.

Place, publisher, year, edition, pages
WORLD SCIENTIFIC PUBL CO PTE LTD, 2018
Keywords
DNA Base Pair Step, Stacking Energy, Density of States, HOMO-LUMO Gap, DFT Calculation
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-351750 (URN)10.1142/S021833901850002X (DOI)000429222700002 ()
Available from: 2018-06-04 Created: 2018-06-04 Last updated: 2018-06-04Bibliographically approved
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