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Tang, H., Gao, X., Zhang, J., Gao, B., Zhou, W., Yan, B., . . . Gou, H. (2020). Boron-Rich Molybdenum Boride with Unusual Short-Range Vacancy Ordering, Anisotropic Hardness, and Superconductivity. Chemistry of Materials, 32(1), 459-467
Open this publication in new window or tab >>Boron-Rich Molybdenum Boride with Unusual Short-Range Vacancy Ordering, Anisotropic Hardness, and Superconductivity
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2020 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 32, no 1, p. 459-467Article in journal (Refereed) Published
Abstract [en]

Determination of the structures of materials involving more light elements such as boron-rich compounds is challenging and technically important in understanding their varied compositions and superior functionalities. Here we resolve the long-standing uncertainties in structure and composition about the highest boride (termed MoB4, Mo1-xB3, or MoB3) through the rapid formation of large sized boron-rich molybdenum boride under pressure. Using high-quality single-crystal X-ray diffraction analysis and aberration-corrected scanning transmission electron microscopy, we reveal that boron-rich molybdenum boride with a composition of Mo0.757B3 exhibits P6(3)/mmc symmetry with a partial occupancy of 0.514 in 211 Mo sites (Mol), and direct observations reveal the short-range ordering of cation vacancies in (010) crystal planes. Large anisotropic Young's moduli and Vickers hardness are seen for Mo0.757B3, which may be attributed by its two-dimensional boron distributions. Mo0.757B3 is also found to be superconducting with a transition temperature (T-c) of 2.4 K, which was confirmed by measurements of resistivity and magnetic susceptibility. Theoretical calculations suggest that the partial occupancy of Mo atoms plays a crucial role in the emergence of superconductivity.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2020
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-406060 (URN)10.1021/acs.chemmater.9b04052 (DOI)000507721600046 ()
Funder
The Swedish Foundation for International Cooperation in Research and Higher Education (STINT)
Available from: 2020-03-04 Created: 2020-03-04 Last updated: 2020-03-04Bibliographically approved
Bouziani, I., Kibbou, M., Haman, Z., Benhouria, Y., Essaoudi, I., Ainane, A. & Ahuja, R. (2020). Electronic and optical properties of ZnO nanosheet doped and codoped with Be and/or Mg for ultraviolet optoelectronic technologies: density functional calculations. Physica Scripta, 95(1), Article ID 015804.
Open this publication in new window or tab >>Electronic and optical properties of ZnO nanosheet doped and codoped with Be and/or Mg for ultraviolet optoelectronic technologies: density functional calculations
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2020 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 95, no 1, article id 015804Article in journal (Refereed) Published
Abstract [en]

Theoretically, the density functional calculations have been effectuated for investigating electronic and optical properties of zinc oxide nanosheet doped and codoped with Be and/or Mg utilizing the generalized gradient approximation modified Becke-Johnson (GGA-mBJ) approach. The computed results show that the ZnBeO, ZnMgO and ZnBeMgO in nanosheet structure, referring to their low formation energy values, are more stable than those in bulk one. Furthermore, the bandgap of ZnO monolayer can be effectively modulated through substitution of Zn atoms by Be and/or Mg. In addition to that, by incorporating Be and/or Mg, the absorption peaks of ZnO nanosheet shift into the shorter UV-wavelength side as well as its reflectivity becomes lower. These results indicate that doping and codoping process of ZnO monolayer with Be and/or Mg are two efficient ways to modulate electronic and optical properties for ultraviolet optoelectronic technologies.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2020
Keywords
ZnO monolayer, substitution process, bandgap modulation, ultraviolet absorption, optoelectronic technologies
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-407619 (URN)10.1088/1402-4896/ab461a (DOI)000515324400002 ()
Funder
Swedish Research Council, 348-2011-7264
Available from: 2020-03-31 Created: 2020-03-31 Last updated: 2020-03-31Bibliographically approved
Benhouria, Y., Lamarti, B., Oubelkacem, A., Essaoudi, I., Ainane, A. & Ahuja, R. (2020). Examination of the Magnetic Properties of the Triangular Type Mixed spin-(1/2,1) Nanowire. Journal of Superconductivity and Novel Magnetism, 33(3), 817-824
Open this publication in new window or tab >>Examination of the Magnetic Properties of the Triangular Type Mixed spin-(1/2,1) Nanowire
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2020 (English)In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, E-ISSN 1557-1947, Vol. 33, no 3, p. 817-824Article in journal (Refereed) Published
Abstract [en]

In the presence of the crystal field D/J(Core) and the external magnetic field h/J(Core), using the Monte Carlo (MC) simulation based on the heat bath algorithm and the effective field theory (EFT), the triangular mixed spin nanowire model consisting of a spin-(1/2) core which is encircled by a spin-1 ferrimagnetic surface shell is studied. We have studied the special effects of the core surface and crystal field on the critical and compensation temperatures. Several properties, such as the magnetization, hysteresis behaviors, coercive field, and remanent magnetizations are studied. For the appropriate values of the system parameters, the compensation point and multi-loops are found PACS 05.50. + q; 77.80. Bh.

Place, publisher, year, edition, pages
SPRINGER, 2020
Keywords
Phase transition, Nanowires, Hysteresis loop, Mixed system, Ising model, Monte Carlo method
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-407962 (URN)10.1007/s10948-019-05270-x (DOI)000515185300026 ()
Available from: 2020-04-02 Created: 2020-04-02 Last updated: 2020-04-02Bibliographically approved
Roondhe, B., Jha, P. K. & Ahuja, R. (2020). Haeckelite boron nitride as nano sensor for the detection of hazardous methyl mercury. Applied Surface Science, 506, Article ID 144860.
Open this publication in new window or tab >>Haeckelite boron nitride as nano sensor for the detection of hazardous methyl mercury
2020 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 506, article id 144860Article in journal (Refereed) Published
Abstract [en]

A new two-dimensional (2D) member in the boron nitride family, haeckelite BN (haeck-BN) is proposed as a nanosensor for the detection of environmental hazardous material, methyl mercury (CH3Hg). Using first principles-based dispersion corrected density functional calculations, we have studied interaction of CH3Hg with haeck-BN to understand its role as toxic gas sensor. The interaction of CH3Hg with haeck-BN is validated by calculating the adsorption energy and electronic density of states (DOS). The change in DOS and work function (WF) upon adsorption of CH3Hg molecules further confirms the sensing ability of haeck-BN. In the pristine form, haeck-BN shows weak interaction towards CH3Hg with adsorption energy of - 0.45 eV. To tune the sensing and electronic properties of haeck-BN, we doped haeck-BN with Al, S, Si, and P atoms. The substitutions were found to alter the electronic properties of haeck-BN, turning it from semiconducting to metallic. However, with the substitution of heteroatom, a significant increment in the adsorption energy is observed in the range of -1.9 eV to - 3.8 eV. Our finding suggests that haeck-BN can be utilized as a sensor for the detection of hazardous toxins.

Place, publisher, year, edition, pages
ELSEVIER, 2020
Keywords
Haeckelite BN, Methyl mercury, Electronic properties, Adsorption, Sensor, Density functional theory
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-407295 (URN)10.1016/j.apsusc.2019.144860 (DOI)000512983600003 ()
Available from: 2020-03-23 Created: 2020-03-23 Last updated: 2020-03-23Bibliographically approved
Deshpande, S. S., Deshpande, M. D., Hussain, T. & Ahuja, R. (2020). Investigating CO2 storage properties of C2N monolayer functionalized with small metal clusters. Journal of CO2 Utilization, 35, 1-13
Open this publication in new window or tab >>Investigating CO2 storage properties of C2N monolayer functionalized with small metal clusters
2020 (English)In: Journal of CO2 Utilization, ISSN 2212-9820, E-ISSN 2212-9839, Vol. 35, p. 1-13Article in journal (Refereed) Published
Abstract [en]

By using first principles calculations based on density functional theory (DFT), we studied a mechanism for the efficient capture of multiple CO2 molecules on TMn doped C2N monolayer (TMn = Ti-n and Sc-n with n = 1-3). A comprehensive analysis revealed that all the metal clusters bind strongly to C2N monolayer; however the bindings of Sc-n are stronger than those of Ti-n clusters. On the basis of electronic structure calculations, it was found that uniformly distributed metal clusters transformed the semiconducting C2N monolayers into metal. The magnetic states of C2N also changed from non-magnetic to magnetic upon the introduction of metal dopants. We found that a maximum of six CO2 molecules could be adsorbed on C2N doped with dimers and trimers of both Sc and Ti clusters. Our van der Waals corrected DFT calculations showed that the average binding energies per CO2 molecule decreased with the increase in the number of incident CO2 molecules to metal functionalized C2N. Overall, Sc-n doped C2N monolayer anchored the CO2 molecules stronger than that of Ti-n doping. We believe that these findings would pave the way for the synthesis of efficient CO2 capture medium.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Doping, Monolayer, Metal clusters, Adsorption, Dimers and trimers
National Category
Theoretical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-402395 (URN)10.1016/j.jcou.2019.08.014 (DOI)000504484800001 ()
Funder
Swedish Research CouncilCarl Tryggers foundation
Available from: 2020-01-16 Created: 2020-01-16 Last updated: 2020-01-16Bibliographically approved
Das, A., Singh, D., Saini, C. P., Ahuja, R., Kaur, A. & Aliukov, S. (2020). Orbital hybridization-induced band offset phenomena in NixCd1-xO thin films. Nanoscale, 12(2), 669-686
Open this publication in new window or tab >>Orbital hybridization-induced band offset phenomena in NixCd1-xO thin films
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2020 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 12, no 2, p. 669-686Article in journal (Refereed) Published
Abstract [en]

Herein, we present the cationic impurity-assisted band offset phenomena in NixCd1-xO (x = 0, 0.02, 0.05, 0.1, 0.2, 0.4, 0.8, and 1) thin films and further discuss them based on orbital hybridization modification. The compositional and structural studies revealed that the cationic substitution of Cd2+ by Ni2+ ions leads to a monotonic shift in the (220) diffraction peak, indicating the suppression of lattice distortion, while the evolution of local strain with an increase in Ni concentration is mainly associated with the mismatch in the electronegativity of the Cd2+ and Ni2+ ions. In fact, Fermi level pinning towards the conduction band minimum takes place with an increase in the Ni concentration at the cost of electronically compensated oxygen vacancies, resulting in the modification of the distribution of carrier concentration, which eventually affects the band edge effective mass of the conduction band electrons and further endorses band gap renormalization. Besides, the appearance of a longitudinal optical (LO) mode at 477 cm(-1), as manifested by Raman spectroscopy, also indicates the active involvement of electron-phonon scattering, whereas modification in the local coordination environment, particularly anti-crossing interaction in conjunction with the presence of satellite features and shake-up states with Ni doping, was confirmed by X-ray absorption near-edge and X-ray photoelectron spectroscopy studies. These results manifest the gradual reduction of orbital hybridization upon the incorporation of Ni, leading to a decrement in the band edge effective electron mass. Finally, the molecular dynamics simulation reflected a 13% reduction in the lattice parameter for the NiO thin film compared to the undoped film, while the projected density of states calculation further supports the experimental observation of reduced orbital hybridization with an increase in Ni concentration.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2020
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-406203 (URN)10.1039/c9nr05184h (DOI)000507642000016 ()31829381 (PubMedID)
Funder
Swedish Research CouncilCarl Tryggers foundation
Available from: 2020-03-06 Created: 2020-03-06 Last updated: 2020-03-06Bibliographically approved
Panda, P. K., Grigoriev, A., Mishra, Y. K. & Ahuja, R. (2020). Progress in supercapacitors: roles of two dimensional nanotubular materials. NANOSCALE ADVANCES, 2(1), 70-108
Open this publication in new window or tab >>Progress in supercapacitors: roles of two dimensional nanotubular materials
2020 (English)In: NANOSCALE ADVANCES, ISSN 2516-0230, Vol. 2, no 1, p. 70-108Article, review/survey (Refereed) Published
Abstract [en]

Overcoming the global energy crisis due to vast economic expansion with the advent of human reliance on energy-consuming labor-saving devices necessitates the demand for next-generation technologies in the form of cleaner energy storage devices. The technology accelerates with the pace of developing energy storage devices to meet the requirements wherever an unanticipated burst of power is indeed needed in a very short time. Supercapacitors are predicted to be future power vehicles because they promise faster charging times and do not rely on rare elements such as lithium. At the same time, they are key nanoscale device elements for high-frequency noise filtering with the capability of storing and releasing energy by electrostatic interactions between the ions in the electrolyte and the charge accumulated at the active electrode during the charge/discharge process. There have been several developments to increase the functionality of electrodes or finding a new electrolyte for higher energy density, but this field is still open to witness the developments in reliable materials-based energy technologies. Nanoscale materials have emerged as promising candidates for the electrode choice, especially in 2D sheet and folded tubular network forms. Due to their unique hierarchical architecture, excellent electrical and mechanical properties, and high specific surface area, nanotubular networks have been widely investigated as efficient electrode materials in supercapacitors, while maintaining their inherent characteristics of high power and long cycling life. In this review, we briefly present the evolution, classification, functionality, and application of supercapacitors from the viewpoint of nanostructured materials to apprehend the mechanism and construction of advanced supercapacitors for next-generation storage devices.

National Category
Energy Systems
Identifiers
urn:nbn:se:uu:diva-407175 (URN)10.1039/c9na00307j (DOI)000508943100002 ()
Funder
Swedish Research Council
Available from: 2020-03-23 Created: 2020-03-23 Last updated: 2020-03-23Bibliographically approved
Panigrahi, P., Kumar, A., Karton, A., Ahuja, R. & Hussain, T. (2020). Remarkable improvement in hydrogen storage capacities of two-dimensional carbon nitride (g-C3N4) nanosheets under selected transition metal doping. International journal of hydrogen energy, 45(4), 3035-3045
Open this publication in new window or tab >>Remarkable improvement in hydrogen storage capacities of two-dimensional carbon nitride (g-C3N4) nanosheets under selected transition metal doping
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2020 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 45, no 4, p. 3035-3045Article in journal (Refereed) Published
Abstract [en]

We have performed DFT simulations to quest for an optimal material for onboard hydrogen (H2) storage applications. Using first-principles calculations, we established that the selected transition metals (M: Sc, Ti, Ni, V) decorated two-dimensional (2D) g-C3N4 sheets as optimal materials with reversible and significantly high H2 gravimetric densities. By effectively avoiding metal-metal (M-M) clustering effect in case of mono doping, up to four molecules of H2 per dopant could be adsorbed with an average binding energy of around 0.30–0.6 eV/H2, which is ideal for practical applications. Decorating the g-C3N4 sheet with (M-M) dimers, the systems are found to be even more efficient for H2 binding than single dopant decoration. The stability of these M decorated g-C3N4 sheets have been confirmed with ab-initio molecular dynamics simulations. We have further calculated the H2 desorption temperatures of metal decorated g-C3N4 sheets, which confirms the practical application of these metal decorated sheets at ambient working conditions.

Keywords
DFT, Monolayers, Adsorption, Metal dopants, Storage capacity
National Category
Condensed Matter Physics Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-407446 (URN)10.1016/j.ijhydene.2019.11.184 (DOI)000513294900052 ()
Funder
Swedish Research CouncilCarl Tryggers foundation Swedish National Infrastructure for Computing (SNIC)Australian Research Council, FT170100373
Available from: 2020-03-25 Created: 2020-03-25 Last updated: 2020-03-25Bibliographically approved
Kibbou, M., Benhouria, Y., Boujnah, M., Essaoudi, I., Ainane, A. & Ahuja, R. (2020). The electronic, magnetic and electrical properties of Mn2FeReO6: Ab-initio calculations and Monte-Carlo simulation. Journal of Magnetism and Magnetic Materials, 495, Article ID UNSP 165833.
Open this publication in new window or tab >>The electronic, magnetic and electrical properties of Mn2FeReO6: Ab-initio calculations and Monte-Carlo simulation
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2020 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 495, article id UNSP 165833Article in journal (Refereed) Published
Abstract [en]

In this paper, a theoretical study of the electronic, magnetic and electrical properties of double perovskite Mn2FeReO6 with a high Curie temperature so far in magnetic oxides was conducted, using several methods such as Ab-initio and Statistical Physics like Monte-Carlo Simulations (MCS). However, the first principles calculations showed a half-metallic behavior from the density of states and band structures calculation, using PBE + U (apply on the elements Mn, Fe, and Re respectively). The critical temperature obtained by MCS has a great similarity with the experimental results.

Place, publisher, year, edition, pages
ELSEVIER, 2020
Keywords
Double perovskite, Density Functional Theory, Semi-metallic, Monte Carlo simulation, Transition temperature
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-397039 (URN)10.1016/j.jmmm.2019.165833 (DOI)000492698500003 ()
Funder
Swedish Research Council, dnr-348-2011-7264
Available from: 2019-11-20 Created: 2019-11-20 Last updated: 2019-11-20Bibliographically approved
Wani, I. H., Jafri, S. H., Wärnå, J., Hayat, A., Li, H., Shukla, V. A., . . . Leifer, K. (2019). A sub 20 nm metal-conjugated molecule junction acting as a nitrogen dioxide sensor. Nanoscale, 11(14), 6571-6575
Open this publication in new window or tab >>A sub 20 nm metal-conjugated molecule junction acting as a nitrogen dioxide sensor
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2019 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 14, p. 6571-6575Article in journal (Refereed) Published
Abstract [en]

The interaction of a gas molecule with a sensing material causes the highest change in the electronic structure of the latter, when this material consists of only a few atoms. If the sensing material consists of a short, conductive molecule, the sensing action can be furthermore probed by connecting such molecules to nanoelectrodes. Here, we report that NO2 molecules that adhere to 4,4'-biphenyldithiol (BPDT) bound to Au surfaces lead to a change of the electrical transmission of the BPDT. The related device shows reproducible, stable measurements and is so far the smallest (<20 nm) gas sensor. It demonstrates modulation of charge transport through molecules upon exposure to nitrogen dioxide down to concentrations of 55 ppb. We have evaluated several devices and exposure conditions and obtained a close to linear dependence of the sensor response on the gas concentration.

National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-381056 (URN)10.1039/c8nr08417c (DOI)000464454400007 ()30916070 (PubMedID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationGöran Gustafsson Foundation for Research in Natural Sciences and MedicineCarl Tryggers foundation Swedish Energy AgencySwedish Foundation for Strategic Research
Available from: 2019-04-03 Created: 2019-04-03 Last updated: 2019-05-03Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1231-9994

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