scholarly journals Lattice parameters and electronic bandgap of orthorhombic potassium sodium niobate K$$_{0.5}$$Na$$_{0.5}$$NbO$$_{3}$$ from density-functional theory

2021 ◽  
Vol 94 (8) ◽  
Author(s):  
Nithin Bidaraguppe Ramesh ◽  
Falko Schmidt ◽  
Arno Schindlmayr
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Nonlinear Behavior ◽  
Lattice Parameters ◽  
Temperature Phase ◽  
Potassium Sodium Niobate ◽  
Virtual Crystal Approximation ◽  
Functional Theory ◽  
Highly Nonlinear ◽  
End Members

Abstract We perform a theoretical analysis of the structural and electronic properties of sodium potassium niobate K$$_{1-x}$$ 1 - x Na$$_{x}$$ x NbO$$_{3}$$ 3 in the orthorhombic room-temperature phase, based on density-functional theory in combination with the supercell approach. Our results for $$x=0$$ x = 0 and $$x=0.5$$ x = 0.5 are in very good agreement with experimental measurements and establish that the lattice parameters decrease linearly with increasing Na contents, disproving earlier theoretical studies based on the virtual-crystal approximation that claimed a highly nonlinear behavior with a significant structural distortion and volume reduction in K$$_{0.5}$$ 0.5 Na$$_{0.5}$$ 0.5 NbO$$_{3}$$ 3 compared to both end members of the solid solution. Furthermore, we find that the electronic bandgap varies very little between $$x=0$$ x = 0 and $$x=0.5$$ x = 0.5 , reflecting the small changes in the lattice parameters. Graphic abstract

scholarly journals Revisiting the zero-temperature phase diagram of stoichiometric SrCoO3 with first-principles methods

2016 ◽  
Vol 18 (44) ◽  
pp. 30686-30695 ◽  
Author(s):  
Pablo Rivero ◽  
Claudio Cazorla
Keyword(s):  
Phase Diagram ◽  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Temperature Phase ◽  
Zero Temperature ◽  
Functional Theory ◽  
Temperature Phase Diagram ◽  
Content Of Oxygen

By using first-principles methods based on density functional theory we revisited the zero-temperature phase diagram of stoichiometric SrCoO3, a ferromagnetic metallic perovskite that undergoes significant structural, electronic, and magnetic changes as its content of oxygen is decreased.

scholarly journals Theoretical calculation for the phonon spectrum and thermodynamic functions of vanadium and its hydride

2021 ◽  
Vol 252 ◽  
pp. 03039
Author(s):  
Qiang Wei-rong ◽  
Wang Xiao-mei ◽  
Liu Wei-qi
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Free Energies ◽  
Generalized Gradient ◽  
Virtual Crystal Approximation ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
Density Functional Perturbation Theory ◽  
Densities Of States

Based on density functional theory(DFT), using virtual crystal approximation and generalized gradient approximation(GGA)with pseudopotential method, the lattices and energies for five crystallines of vanadium hydrides are optimized and calculated. The phonon densities of states are calculated based on density functional perturbation theory(DFPT). The standard Heat capacities, Entropies, Helmholtz free energies and Gibbs functions of vanadium and its hydride are deduced at 298.15K. The calculated results are discussed and compared with experimental data.

scholarly journals Density Functional Theory and Experimental Determination of Band Gaps and Lattice Parameters in Kesterite Cu2ZnSn(SxSe1–x)4

2020 ◽  
Vol 11 (24) ◽  
pp. 10463-10468
Author(s):  
Chuan-Jia Tong ◽  
Holly J. Edwards ◽  
Theodore D. C. Hobson ◽  
Ken Durose ◽  
Vinod R. Dhanak ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Experimental Determination ◽  
Density Functional ◽  
Lattice Parameters ◽  
Band Gaps ◽  
Functional Theory

scholarly journals Quantum Monte Carlo analysis of a charge ordered insulating antiferromagnet: the Ti4O7 Magnéli phase

2016 ◽  
Vol 18 (27) ◽  
pp. 18323-18335 ◽  
Author(s):  
Anouar Benali ◽  
Luke Shulenburger ◽  
Jaron T. Krogel ◽  
Xiaoliang Zhong ◽  
Paul R. C. Kent ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Quantum Monte Carlo ◽  
Density Functional ◽  
Ferromagnetic State ◽  
Monte Carlo Analysis ◽  
Temperature Phase ◽  
Antiferromagnetic State ◽  
Functional Theory ◽  
A Charge ◽  
Low Temperature Phase

Spin density surfaces in the low temperature phase of Ti4O7: the ferromagnetic state (left panel), and the lowest-energy antiferromagnetic state (right panel). The figures were generated using self-interaction corrected density functional theory.

Electronic and Structural Properties of Ferromagnetic Shape Memory Alloys Studied by Density Functional Theory

2008 ◽  
Vol 52 ◽  
pp. 165-174 ◽  
Author(s):  
Aparna Chakrabarti ◽  
S.R. Barman
Keyword(s):  
Density Functional Theory ◽  
Structural Properties ◽  
Density Functional ◽  
Magnetic Moments ◽  
Temperature Phase ◽  
Martensitic Transition ◽  
Ferromagnetic Shape Memory Alloys ◽  
Functional Theory ◽  
Ferromagnetic Shape Memory ◽  
Electronic And Structural Properties

The electronic and structural properties of different members of the Ni-Mn-Ga family calculated by ab initio density functional theory are discussed. From total energy calculations, we show that the martensitic phase is the stable low temperature phase. Moreover, occurrence of ferromagnetic and paramagnetic martensitic phases for Ni2MnGa and Ni2.25Mn0.75Ga, respectively, are explained. Modifications in the density of states near the Fermi level EF are observed across the martensitic transition for Ni2MnGa, as well as in Mn2NiGa. While Ni2MnGa is ferromagnetic, we find Mn2NiGa to be ferrimagnetic. The calculated lattice constants and the magnetic moments are in good agreement with experiment.

scholarly journals Density functional theory calculations of merohedric twinning in KLiSO4

2019 ◽  
Vol 234 (4) ◽  
pp. 211-217
Author(s):  
Hans Grimmer ◽  
Bernard Delley
Keyword(s):  
Density Functional Theory ◽  
Aqueous Solutions ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Energy Difference ◽  
Boundary Plane ◽  
Temperature Phase ◽  
Functional Theory ◽  
Transformation Twins ◽  
Polysynthetic Twin

Abstract Density functional theory (DFT) calculations have been performed on five models of periodic, polysynthetic twin interfaces in the ambient-temperature phase of KLiSO4, which has space group P63. The models represent the three merohedric twin laws (m||z, 2⊥z and 1̅) with boundary plane (1 0 1̅ 0), also with boundary plane (0 0 0 1) in case of m, and with boundary plane (1 2̅ 1 0) in case of 1̅. The models satisfy stoichiometry at the boundary plane and maintain the fourfold coordination of the Li and S atoms and the twofold coordination of the oxygen atoms. Relaxed lattice parameters and atomic positions were determined by DFT, using the DMol3 code with functional PBEsol. The energy difference between polysynthetic twin and single crystal per primitive cell of the twin is 0.0009 eV for m(0 0 0 1), 0.09 eV for 1̅(1 0 1̅ 0), 0.58 eV for m(1 0 1̅ 0) and 0.55 eV for 2(1 0 1̅ 0). In KLiSO4 crystals grown from aqueous solutions the first twin was frequently observed, similarly also the second twin in Cr-doped crystals, whereas the third twin appeared only rarely and the fourth was not observed. Not only for KLiSO4 but also for quartz, the energy of twins and the frequency of their occurrence are closely connected for crystals grown from aqueous solutions, whereas for the formation of transformation twins the availability of twin nuclei plays a major role.

scholarly journals Новая возможная структура силицида Mg-=SUB=-2-=/SUB=-Si под давлением

2018 ◽  
Vol 60 (5) ◽  
pp. 864
Author(s):  
Ю.В. Луняков
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Lattice Parameters ◽  
Evolutionary Search ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Symmetry Structure ◽  
Experimental Values ◽  
Low Symmetry

AbstractAs a result of an evolutionary search based on the density functional theory, a new low-symmetry structure of silicide Mg_2Si under pressure was discovered. This structure can exist along with the known structures of the symmetry Pnma and P63/mmc and is stable at a pressure of about 20 GPa. The lattice parameters of the discovered structure are in better agreement with the experimental values than the lattice parameters of the known structures.

Pd Segregation at (001) B2-NiSi/Si Epitaxial Interface Studied by Density Functional Theory

2008 ◽  
Vol 1079 ◽  
Author(s):  
Dae-Hee Kim ◽  
Hwa-Il Seo ◽  
Yeong-Cheol Kim
Keyword(s):  
Density Functional Theory ◽  
Energy Minimization ◽  
Density Functional ◽  
Lattice Parameters ◽  
Functional Theory ◽  
Epitaxial Interface

ABSTRACTPd segregation at (001) B2-NiSi/Si epitaxial interface was studied by using density functional theory (DFT). An epitaxial interface between 2×2×4 (001) B2-NiSi supercell and 1×1×2 (001) Si supercell was first constructed by adjusting the lattice parameters of B2-NiSi structure to be matched with those of Si structure. We chose Ni atoms as terminating layer of the B2-NiSi, and an equilibrium gap between the B2-NiSi and Si was calculated to be 1.1 Å. The Ni atoms in the structure moved away from the original positions along z-direction in a systematic way during the energy minimization. Two different Ni sites were identified at the interface and the bulk, respectively. The Ni sites at the interface farther away from the interface were more favorable for Pd substitution.

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