Herein, we report the phase stability of the hydrogenated Ti2C MXene monolayer using an evolutionary algorithm based on the density functional theory. We predict the existence of the hexagonal Ti2CH,...
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This work reports the ab initio study of the crystal energetics, electronic properties, mechanical properties, and the impacts of strain on electronic properties of Mo2CT2 (T = O, F, and Cl).
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Ab initio study of high-pressure phase transition and electronic structure of Fe-doped CeO2 with Fe concentrations of 3.125, 6.25, and 12.5 at% has been reported. At a constant-pressure consideration, the lattice constants and the volume... more
Ab initio study of high-pressure phase transition and electronic structure of Fe-doped CeO2 with Fe concentrations of 3.125, 6.25, and 12.5 at% has been reported. At a constant-pressure consideration, the lattice constants and the volume of the supercell were decreased with an increasing concentration of Fe. The average bond length of Fe–O is lower than that of Ce–O. As a result, Fe doping induces the reduced volume of the cell, which is in good agreement with previous experiments. At high pressure (~ 30 GPa), it was found that the transition pressure from the fluorite to the cotunnite orthorhombic phase decreases at a higher concentration of Fe, indicating that the formation energy of the compound is induced by Fe-doping. Furthermore, compression leads to interesting electronic properties too. Under higher pressures, the bandgap increases in the cubic structure under compression and then suddenly plummets after the transition to the orthorhombic phase. The 3d states of Fe mainly in...
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Abstract We have predicted the hexagonal close-packed (hcp) structure of bismuth (Bi) using ab initio random structure searching (AIRSS) at extreme conditions. The calculation, which included spin–orbit coupling, shows that the hcp... more
Abstract We have predicted the hexagonal close-packed (hcp) structure of bismuth (Bi) using ab initio random structure searching (AIRSS) at extreme conditions. The calculation, which included spin–orbit coupling, shows that the hcp structure is thermodynamically and dynamically stable at high pressure. The electronic band structure calculations suggest the downshifting of the flat band through compression due to Lifshitz transitions. The Fermi surface shape of hcp Bi produces the metallicity in this material. The electron localization function reveals a weak bonding of Bi. The solutions of electronic topological transition and a soft-mode of phonon dispersion provide the possibility for prediction and reduction of the superconducting transition temperature.
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The structural phase transition and electronic properties of Li2O2under pressures up to 500 GPa have been investigated using first-principles calculations.
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ABSTRACT An ab initio study of structural phase transformations and band structure under high pressure was performed on a ternary semiconductor, AgInTe2. Based on DFT within both LDA and GGA exchange-correlation, US-PP, and plane wave... more
ABSTRACT An ab initio study of structural phase transformations and band structure under high pressure was performed on a ternary semiconductor, AgInTe2. Based on DFT within both LDA and GGA exchange-correlation, US-PP, and plane wave basis set, were employed for this work. Transition pressures and calculated parameters with transformation pathway was identified to be; chalcopyrite→cd-B1→cd-Cmcm, were in good agreement with experiments. We also predicted a higher pressure phase based on supercell with size 2×2×2 of B2 structure in which all the configuration of cation structures were accounted to compare and clarify its׳cations-disordered state. The predicted structure probably appeared at around 40 GPa from cd-Cmcm to cd-B2. In the case of band structure calculation, NC-PP in which 4p10 electrons of In were not treated, was also employed in chalcopyrite at a pressure range of 0–4 GPa to improve a very narrow band gap of US-PP, and this failure will be discussed. Partial density of state (PDOS), and electronic population analysis were also calculated to finely investigate the electronic transition around the Fermi level. Our calculated results were in good agreement with experiments. The direct energy gap (Eg) was linearly proportional to pressure with increasing rate of 46.4 and 44.6 meV/GPa. In addition, at ambient conditions, Eg was equal to 1.02 eV and 0.95 eV for GGA and LDA, respectively. Band structure from all the calculations have shown a higher second band gap (View the MathML source) which could occur due to crystal-field splitting.
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ABSTRACT We constructed ZnO nanorods combining energy of surface and core atoms within B4 and B1 phases. Their morphologies were directly built up based on previous experiments and transformation path. ZnO nanorods were varied in diameter... more
ABSTRACT We constructed ZnO nanorods combining energy of surface and core atoms within B4 and B1 phases. Their morphologies were directly built up based on previous experiments and transformation path. ZnO nanorods were varied in diameter and length. By using density functional theory with GGA exchange-correlation functional, the surfaces were cleaved from the optimized crystal structures at various different pressures in both B4 and B1 phases. A slab model with a fixed top atomic layer was employed to achieve the surfaces under high pressure. The finding shows transition pressure increases with decreasing diameter and as well as increasing length of nanorods, which is in good agreement with previous experiments.
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First principles-based electronic structure calculations of superhard iron tetraboride (FeB4) under high pressure have been undertaken in this study. Starting with a "conventional" superconducting phase of this material under... more
First principles-based electronic structure calculations of superhard iron tetraboride (FeB4) under high pressure have been undertaken in this study. Starting with a "conventional" superconducting phase of this material under high pressure leads to an unexpected phase transition toward a semiconducting one. This transition occurred at 53.7 GPa, and this pressure acts as a demarcation between two distinct crystal symmetries, metallic orthorhombic and semiconducting tetragonal phases, with Pnnm and I4₁/acd space groups, respectively. In this work, the electron-phonon coupling-derived superconducting T(c) has been determined up to 60 GPa and along with optical band gap variation with increasing pressure up to 300 GPa. The dynamic stability has been confirmed by phonon dispersion calculations throughout this study.
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The structural phase transformations in the chalcopyrite semiconductor AgInTe2 have been studied up to 10 GPa on both pressure increase and decrease. The experiments were conducted using angle-dispersive X-ray diffraction with synchrotron... more
The structural phase transformations in the chalcopyrite semiconductor AgInTe2 have been studied up to 10 GPa on both pressure increase and decrease. The experiments were conducted using angle-dispersive X-ray diffraction with synchrotron radiation and an image plate. The diffraction patterns of AgInTe2 at ambient pressure reveal two coexisting phases: the first has the chalcopyrite structure while the second has a
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The complex and unusual high-pressure phase transition of III-A (i.e. Al, Ga, and In) metals have been investigated in the last several decades because of their interesting periodic table position between the elements having metallic and... more
The complex and unusual high-pressure phase transition of III-A (i.e. Al, Ga, and In) metals have been investigated in the last several decades because of their interesting periodic table position between the elements having metallic and covalent bonding. Our present first principles-based electronic structure calculations and experimental investigation have revealed the unusual distortion in face-centered cubic (f.c.c.) phase of the heavy element thallium (Tl) induced by the high pressure. We have predicted body-centered tetragonal (b.c.t) phase at 83 GPa using an evolutionary algorithm coupled with ab initio calculations, and this prediction has been confirmed with a slightly distorted parameter ([Formula: see text] × a - c)/c lowered by 1% using an angle-dispersive X-ray diffraction technique. The density functional theory (DFT)-based calculations suggest that s-p mixing states and the valence-core overlapping of 6s and 5d states play the most important roles for the phase transi...