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Hussain, T., Vovusha, H., Kaewmaraya, T., Amornkitbamrung, V. & Ahuja, R. (2018). Adsorption characteristics of DNA nucleobases, aromatic amino acids and heterocyclic molecules on silicene and germanene monolayers. Sensors and actuators. B, Chemical, 255, 2713-2720
Open this publication in new window or tab >>Adsorption characteristics of DNA nucleobases, aromatic amino acids and heterocyclic molecules on silicene and germanene monolayers
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2018 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 255, p. 2713-2720Article in journal (Refereed) Published
Abstract [en]

Binding of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules on two-dimensional silicene and germanene sheets have been investigated for the application of sensing of biomolecules using first principle density functional theory calculations. Binding energy range for nucleobases, amino acids and heterocyclic molecules with both the sheets have been found to be (0.43-1.16 eV), (0.70-1.58 eV) and (0.22-0.96 eV) respectively, which along with the binding distances show that these molecules bind to both sheets by physisorption and chemisorption process. The exchange of electric charges between the monolayers and the incident molecules has been examined by means of Bader charge analysis. It has been observed that the introduction of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules alters the electronic properties of both silicene and germanene nano sheets as studied by plotting the total (TDOS) and partial (PDOS) density of states. The DOS plots reveal the variation in the band gaps of both silicene and germanene caused by the introduction of studied molecules. Based on the obtained results we suggest that both silicene and germanene monolayers in their pristine form could be useful for sensing of biomolecules.

Keyword
Adsorption characteristics, DNA nucleobases, Aromatic amino acids, Heterocyclic molecules
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-341967 (URN)10.1016/j.snb.2017.09.083 (DOI)000414686500032 ()
Funder
Swedish Research CouncilCarl Tryggers foundation StandUp
Available from: 2018-02-19 Created: 2018-02-19 Last updated: 2018-02-19Bibliographically approved
Das, S., Swain, D., Araujo, R. B., Shi, S., Ahuja, R., Row, T. N. G. & Bhattacharyya, A. J. (2018). Alloying in an Intercalation Host: Metal Titanium Niobates as Anodes for Rechargeable Alkali-Ion Batteries. Chemistry - An Asian Journal, 13(3), 299-310
Open this publication in new window or tab >>Alloying in an Intercalation Host: Metal Titanium Niobates as Anodes for Rechargeable Alkali-Ion Batteries
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2018 (English)In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 13, no 3, p. 299-310Article in journal (Refereed) Published
Abstract [en]

We discuss here a unique flexible non-carbonaceous layered host, namely, metal titanium niobates (M-Ti-niobate, M: Al3+, Pb2+, Sb3+, Ba2+, Mg2+), which can synergistically store both lithium ions and sodium ions via a simultaneous intercalation and alloying mechanisms. M-Ti-niobate is formed by ion exchange of the K+ ions, which are specifically located inside galleries between the layers formed by edge and corner sharing TiO6 and NbO6 octahedral units in the sol-gel synthesized potassium titanium niobate (KTiNbO5). Drastic volume changes (approximately 300-400%) typically associated with an alloying mechanism of storage are completely tackled chemically by the unique chemical composition and structure of the M-Ti-niobates. The free space between the adjustable Ti/Nb octahedral layers easily accommodates the volume changes. Due to the presence of an optimum amount of multivalent alloying metal ions (50-75% of total K+) in the M-Ti-niobate, an efficient alloying reaction takes place directly with ions and completely eliminates any form of mechanical degradation of the electroactive particles. The M-Ti-niobate can be cycled over a wide voltage range (as low as 0.01V) and displays remarkably stable Li+ and Na+ ion cyclability (>2 Li+/Na+ per formula unit) for widely varying current densities over few hundreds to thousands of successive cycles. The simultaneous intercalation and alloying storage mechanisms is also studied within the density functional theory (DFT) framework. DFT expectedly shows a very small variation in the volume of Al-titanium niobate following lithium alloying. Moreover, the theoretical investigations also conclusively support the occurrence of the alloying process of Li ions with the Al ions along with the intercalation process during discharge. The M-Ti-niobates studied here demonstrate a paradigm shift in chemical design of electrodes and will pave the way for the development of a multitude of improved electrodes for different battery chemistries.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2018
Keyword
alloying, anode, intercalation, rechargeable battery, synergy
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-345713 (URN)10.1002/asia.201701602 (DOI)000424106500016 ()29280560 (PubMedID)
Funder
Swedish Research CouncilStandUp
Available from: 2018-03-14 Created: 2018-03-14 Last updated: 2018-03-14Bibliographically approved
Pandey, K., Singh, D., Gupta, S. K., Yadav, P., Sonvane, Y., Lukacevic, I., . . . Ahuja, R. (2018). Improving electron transport in the hybrid perovskite solar cells using CaMnO3-based buffer layer. Nano Energy, 45, 287-297
Open this publication in new window or tab >>Improving electron transport in the hybrid perovskite solar cells using CaMnO3-based buffer layer
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2018 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 45, p. 287-297Article in journal (Refereed) Published
Abstract [en]

In the present article, the detailed analyses of interface properties and device performance of inorganic perovskite CaMnO3-based buffer layer hybrid perovskite solar cell have been undertaken. Analyses are based on ab initio simulations and macroscopic modelling. A thorough study of electronic and optical properties and interface charge dynamics revealed that CaMnO3 presents a better candidate for the electron transport material in thin film hole transporting material free hybrid perovskite solar cells with the planar architecture than the most common anatase TiO2. This result is founded on the more appropriate band gap and better band alignment with the hybrid perovskite, leading to the faster charge carrier mobility, improved charge transfer and reduced exciton recombination. The results from theoretical simulations are justified by the solar cell model, which explored the basic cell characteristics and parameters: open circuit voltage, short circuit current, fill factor and efficiency, as the functions of cell performance factors, like defect density, diffusion length, absorber layer thickness and band offset. Our model suggests an unoptimized device with a photo-conversion efficiency of almost 10% for the low defect concentrations under 10(15). With efficiency in the upper range for HTM free perovskite solar cells, we propose that the CaMnO3-based solar cell poses as an improvement upon the up to now most frequently used ones and provides important step toward their commercialisation.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keyword
Perovskite solar cell, Electron transport layer, Charge transfer, Interface junction, Density functional theory
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-348844 (URN)10.1016/j.nanoen.2018.01.009 (DOI)000425396400032 ()
Funder
Swedish Research Council
Available from: 2018-04-23 Created: 2018-04-23 Last updated: 2018-04-23Bibliographically approved
Shi, S., Zhu, L., Zhang, H., Sun, Z. & Ahuja, R. (2018). Mapping the relationship among composition, stacking fault energy and ductility in Nb alloys: A first-principles study. Acta Materialia, 144, 853-861
Open this publication in new window or tab >>Mapping the relationship among composition, stacking fault energy and ductility in Nb alloys: A first-principles study
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2018 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 144, p. 853-861Article in journal (Refereed) Published
Abstract [en]

Transition metals (TMs) are extensively used to improve the mechanical properties of niobium based alloy, one of the most promising high-temperature materials. Yet the microscopic mechanism of the alloying effects of these transition metals on the mechanical properties is unclear. In this study, we have mapped out the composition-SFE-ductility relationship for TM-alloyed Nb systems by comprehensively investigating the unstable stacking fault energies (SFEs), gamma(us), and the ductility in binary and ternary Nb alloys using the first-principles calculations. It is found that the valence electron concentration can be used as the key descriptor to evaluate the SFE of Nb matrix, which is applicable to both binary and ternary alloys. The microscopic mechanism arises from the electron redistribution in the local stacking fault area. Moreover, for ternary Nb-Ti based alloys, the interaction between Ti and the third alloying elements has negligible effect on the SFE of the systems, and the valence-electron rule still dominates. The alloying effects on the ductility are further illustrated based on the ratio between surface energies and SFEs. The composition-SFE-ductility map obtained by our theoretical calculations is calibrated by available experimental data.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keyword
Stacking-fault energy, Mechanical alloying, Ductility, First-principles calculations
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-347092 (URN)10.1016/j.actamat.2017.11.029 (DOI)000424067100078 ()
Available from: 2018-03-26 Created: 2018-03-26 Last updated: 2018-03-26Bibliographically approved
Yang, X., Li, H., Hu, M., Liu, Z., Wärnå, J., Cao, Y., . . . Luo, W. (2018). Mechanical properties investigation on single-wall ZrO2 nanotubes: A finite element method with equivalent Poisson's ratio for chemical bonds. Physica. E, Low-Dimensional systems and nanostructures, 98, 23-28
Open this publication in new window or tab >>Mechanical properties investigation on single-wall ZrO2 nanotubes: A finite element method with equivalent Poisson's ratio for chemical bonds
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2018 (English)In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 98, p. 23-28Article in journal (Refereed) Published
Abstract [en]

A method to obtain the equivalent Poisson's ratio in chemical bonds as classical beams with finite element method was proposed from experimental data. The UFF (Universal Force Field) method was employed to calculate the elastic force constants of Zr-O bonds. By applying the equivalent Poisson's ratio, the mechanical properties of single-wall ZrNTs (ZrO2 nanotubes) were investigated by finite element analysis. The nanotubes' Young's modulus (Y), Poisson's ratio (nu) of ZrNTs as function of diameters, length and chirality have been discussed, respectively. We found that the Young's modulus of single-wall ZrNTs is calculated to be between 350 and 420 GPa.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keyword
Signal-wall ZrO2 nanotubes, Mechanical properties, Finite element method, Poisson's ratio
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-347532 (URN)10.1016/j.physe.2017.10.005 (DOI)000425118100005 ()
Funder
Swedish Research Council
Available from: 2018-04-04 Created: 2018-04-04 Last updated: 2018-04-04Bibliographically approved
Tsuppayakorn-aek, P., Luo, W., Ahuja, R. & Bovornratanaraks, T. (2018). The High-Pressure Superconducting Phase of Arsenic. Scientific Reports, 8, Article ID 3026.
Open this publication in new window or tab >>The High-Pressure Superconducting Phase of Arsenic
2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 3026Article in journal (Refereed) Published
Abstract [en]

Ab initio random structure searching (AIRSS) technique is predicted a stable structure of arsenic (As). We find that the body-centered tetragonal (bct) structure with spacegroup I4(1)/acd to be the stable structure at high pressure. Our calculation suggests transition sequence from the simple cubic (sc) structure transforms into the host-guest (HG) structure at 41 GPa and then into the bct structure at 81 GPa. The bct structure has been calculated using ab initio lattice dynamics with finite displacement method confirm the stability at high pressure. The spectral function alpha F-2 of the bct structure is higher than those of the body-centered cubic (bcc) structure. It is worth noting that both bct and bcc structures share the remarkable similarity of structural and property. Here we have reported the prediction of temperature superconductivity of the bct structure, with a T-c of 4.2 K at 150 GPa.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-348108 (URN)10.1038/s41598-018-20088-8 (DOI)000424985800064 ()29445106 (PubMedID)
Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2018-04-11Bibliographically approved
Almeida, R., Banerjee, A., Chakraborty, S., Almeida, J. & Ahuja, R. (2018). Theoretical Evidence behind Bifunctional Catalytic Activity in Pristine and Functionalized Al2C Monolayers. ChemPhysChem, 19(1), 148-152
Open this publication in new window or tab >>Theoretical Evidence behind Bifunctional Catalytic Activity in Pristine and Functionalized Al2C Monolayers
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2018 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 19, no 1, p. 148-152Article in journal (Refereed) Published
Abstract [en]

First principles electronic structure calculations based on the density functional theory (DFT) framework are performed to investigate hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on two-dimensional Al2C monolayers. In addition to the pristine Al2C monolayer, monolayers doped with Nitrogen (N), Phosphorous (P), Boron (B), and Sulphur (S) are also investigated. After determining the individual adsorption energy of hydrogen and oxygen on the different functionalized Al2C monolayers, the adsorption free energies are predicted for each of the functionalized monolayers in order to assess their suitability for HER or OER. The density of states and optical absorption spectra calculations along with the work function of the functionalized Al2C monolayers enable us to gain a profound understanding of the electronic structure for the individual system and their relation to the water splitting mechanism.

Keyword
adsorption free energy, Al2C monolayer, bifunctional catalysis, density functional calculations, doping
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-341495 (URN)10.1002/cphc.201700768 (DOI)000419338600020 ()28925531 (PubMedID)
Note

De 2 första författarna delar förstaförfattarskapet.

Available from: 2018-02-19 Created: 2018-02-19 Last updated: 2018-02-19Bibliographically approved
Mir, S. H., Chakraborty, S., Wärnå, J., Narayan, S., Jha, P. C., Jha, P. K. & Ahuja, R. (2017). A comparative study of hydrogen evolution reaction on pseudo-monolayer WS2 and PtS2: insights based on the density functional theory. Catalysis Science & Technology, 7(3), 687-692
Open this publication in new window or tab >>A comparative study of hydrogen evolution reaction on pseudo-monolayer WS2 and PtS2: insights based on the density functional theory
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2017 (English)In: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 7, no 3, p. 687-692Article in journal (Refereed) Published
Abstract [en]

In this study, we investigated the catalytic activity of ultrathin PtS2 and WS2 nanostructures for the hydrogen evolution reaction by electronic structure calculations based on the spin-polarised density functional theory. We also explored the effect of van der Waals interactions on the surface-adsorbate interactions. Using the adsorption free energy of H-2 as an activity descriptor, we tuned the photocatalytic water splitting activity of PtS2 and WS2 by functionalizing the individual systems with different transition metals such as Ru, Rh, Pd, Ag, Ir, Au, and Hg. The density of states was calculated along with the band structure to find the effect of different dopants on the fundamental band gap, which is one of the primary parameters in the photocatalytic water splitting.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-320468 (URN)10.1039/c6cy02426b (DOI)000398053000017 ()
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2017-04-26Bibliographically approved
Qian, Z., Raghubanshi, H., Hudson, M. S., Srivastava, O. N., Liu, X. & Ahuja, R. (2017). Ab initio insight into graphene nanofibers to destabilize hydrazine borane for hydrogen release. Chemical Physics Letters, 669, 110-114
Open this publication in new window or tab >>Ab initio insight into graphene nanofibers to destabilize hydrazine borane for hydrogen release
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2017 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 669, p. 110-114Article in journal (Refereed) Published
Abstract [en]

We report the potential destabilizing effects of graphene nanofibers on the hydrogen release property of hydrazine borane via state-of-the-art ab initio calculations for the first time. Interactions of a hydrazine borane cluster with two types of graphene patch edges which exist abundantly in our synthesized graphene nanofibers have been investigated. It is found that both zigzag and armchair edges can greatly weaken the H-host bonds (especially the middle N-H bond) of hydrazine borane. The dramatic decrease in hydrogen removal energy is caused by the strong interaction between hydrazine borane and the graphene patch edges concerning the electronic charge density redistribution.

Keyword
Energy storage, Destabilization, Nanostructured materials, Density functional theory
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-316940 (URN)10.1016/j.cplett.2016.12.043 (DOI)000392774900016 ()
Funder
Swedish Research Council
Available from: 2017-03-09 Created: 2017-03-09 Last updated: 2017-11-29Bibliographically approved
Sun, W., Luo, W., Feng, Q. & Ahuja, R. (2017). Anisotropic distortion and Lifshitz transition in alpha-Hf under pressure. Physical Review B, 95(11), Article ID 115130.
Open this publication in new window or tab >>Anisotropic distortion and Lifshitz transition in alpha-Hf under pressure
2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 11, article id 115130Article in journal (Refereed) Published
Abstract [en]

In this work we report a theoretical investigation on behavior of the elastic constant C-44 and the transverse optical phonon mode E(2)g of a-Hf under pressure within the density functional theory. In contrast to many other reported transition metals, the above two quantities do not show a synchronous relation as pressure increases. Below 13 GPa, an opposite shifting tendency has been observed. However, once the pressure is raised above 13 GPa, the trend is pulled back to be consistent. This anomalous behavior is figured out to be caused by the large lattice anisotropy of the c/a ratio along with the elastic anisotropy. The synchronous behavior is found to be in accordance with the behavior of c/a ratio with increased pressure. In our band-structure investigations the electronic topological transition has been discovered at 10 GPa, which relates to the change of c/a ratio suggested by recent literature. The presence of the Van Hove singularity shown in the densities of states has been identified and regarded as the origin of the variation of C-44 and E(2)g.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2017
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-320218 (URN)10.1103/PhysRevB.95.115130 (DOI)000396273400004 ()
Funder
Swedish Research Council
Available from: 2017-04-18 Created: 2017-04-18 Last updated: 2017-11-29Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1231-9994

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