scholarly journals The Pseudopotential Approach within Density-Functional Theory: The Case of Atomic Metallic Hydrogen

2020 ◽  
Vol 5 (4) ◽  
pp. 74
Author(s):  
Jin Zhang ◽  
Jeevake Attapattu ◽  
Jeffrey M. McMahon
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Metallic Phase ◽  
Metallic Hydrogen ◽  
Spectral Functions ◽  
Functional Theory ◽  
Phonon Dispersion Curves ◽  
Pseudopotential Approach ◽  
Critical Temperature Tc

Internal energies, enthalpies, phonon dispersion curves, and superconductivity of atomic metallic hydrogen are calculated. The standard use of pseudopotentials in density-functional theory are compared with full Coulomb-potential, all-electron linear muffin-tin orbital calculations. Quantitatively similar results are found as far as internal energies are concerned. Larger differences are found for phase-transition pressures; significant enough to affect the phase diagram. Electron–phonon spectral functions α2F(ω) also show significant differences. Against expectation, the estimated superconducting critical-temperature Tc of the first atomic metallic phase I41/amd (Cs-IV) at 500 GPa is actually higher.

Study of dynamic and thermodynamic properties of zinc-blend and wurtzite cadmium sulfide (CdS) using density functional theory

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Teshome Gerbaba Edossa ◽  
Menberu Mengasha Woldemariam
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Density Functional ◽  
Chemical Potential ◽  
Phonon Dispersion ◽  
Dynamic Properties ◽  
Dielectric Constants ◽  
High Symmetry ◽  
Functional Theory ◽  
Zinc Blend

Abstract The dynamic and thermodynamic properties of wurtzite (wz) and zinc-blend (zb) CdS are investigated within the density functional theory using different approximation methods such as LDA, PBE, and DFT+U. Hellmann–Feynman approach is implemented for the relaxation of atomic position for both phases. To guarantee the accuracy of calculation, the convergence test of total energy with respect to energy cutoff and k-point sampling is performed. The dynamic properties such as phonon dispersion, phonon density of state, frequency along with high symmetry points, static and dynamic polarizability, and dielectric constants are calculated. The obtained values are compared with previous theoretical results. DFT + U approximation gives a good result that is consistent with the available theory. Moreover, the vibrational energy, vibrational free energy, entropy, electron chemical potential, and constant-volume specific heat are obtained within LDA, PBE, and DFT + U approximations.

scholarly journals Electronic and Magnetic Properties of Bulk and Monolayer CrSi2: A First-Principle Study

2018 ◽  
Vol 8 (10) ◽  
pp. 1885 ◽  
Author(s):  
Shaobo Chen ◽  
Ying Chen ◽  
Wanjun Yan ◽  
Shiyun Zhou ◽  
Xinmao Qin ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Density Functional ◽  
Phonon Dispersion ◽  
First Principle ◽  
Metallic Behavior ◽  
Functional Theory ◽  
Phonon Dispersion Curves ◽  
Electronic And Magnetic Properties ◽  
Quantum Size ◽  
Spin Polarized

We investigated the electronic and magnetic properties of bulk and monolayer CrSi2 using first-principle methods based on spin-polarized density functional theory. The phonon dispersion, electronic structures, and magnetism of bulk and monolayer CrSi2 were scientifically studied. Calculated phonon dispersion curves indicated that both bulk and monolayer CrSi2 were structurally stable. Our calculations revealed that bulk CrSi2 was an indirect gap nonmagnetic semiconductor, with 0.376 eV band gap. However, monolayer CrSi2 had metallic and ferromagnetic (FM) characters. Both surface and confinement effects played an important role in the metallic behavior of monolayer CrSi2. In addition, we also calculated the magnetic moment of unit cell of 2D multilayer CrSi2 nanosheets with different layers. The results showed that magnetism of CrSi2 nanosheets was attributed to band energy between layers, quantum size, and surface effects.

Theoretical investigation of elastic and phononic properties of Zn1−xBexO alloys

2015 ◽  
Vol 29 (24) ◽  
pp. 1550140 ◽  
Author(s):  
F. Elhamra ◽  
S. Lakel ◽  
M. Ibrir ◽  
K. Almi ◽  
H. Meradji
Keyword(s):  
Density Functional ◽  
Phonon Dispersion ◽  
Local Density ◽  
Molar Fraction ◽  
Dielectric Constants ◽  
Functional Theory ◽  
Phonon Dispersion Curves ◽  
Density Functional Perturbation Theory ◽  
Pseudo Potential ◽  
Born Effective Charge

Our calculations were conducted within density functional theory (DFT) and density functional perturbation theory (DFPT) using norm-conserving pseudo-potential and the local density approximation. The elastic constants of [Formula: see text] were calculated, [Formula: see text], [Formula: see text] and [Formula: see text] increase with the increase of Be content, whereas the [Formula: see text] shows a non-monotonic variation and [Formula: see text] decreases when Be concentration increases. The values of bulk modulus [Formula: see text], Young’s modulus [Formula: see text] and shear modulus [Formula: see text] increase with the increase of Be content. Poisson’s ratio [Formula: see text] decreases with increased Be concentration. The ductility decreases with increasing Be concentration and the compressibility for [Formula: see text] along [Formula: see text]-axis is smaller than along [Formula: see text]-axis. Phonon dispersion curves show that [Formula: see text] is dynamically stable (no soft modes). Quantities such as refractive index, Born effective charge, dielectric constants and optical phonon frequencies were calculated as a function of the Be molar fraction [Formula: see text]. The agreement between the present results and the known data that are available only for ZnO and BeO is generally satisfactory. Our results for [Formula: see text] [Formula: see text] are predictions.

Computational investigations of MnNiCuSb alloy for structural, elasto-mechanical and vibrational properties

2019 ◽  
Vol 33 (23) ◽  
pp. 1950276
Author(s):  
Abu Bakar ◽  
Maaz Afzal ◽  
Muzaffar Bashir ◽  
A. Afaq ◽  
Aneeza Iftikhar ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dispersion Curve ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Phonon Dispersion Curve ◽  
Vibrational Properties ◽  
Type I ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Anisotropic Factor

The MnNiCuSb Quaternary Heusler Alloy (QHA) in Y-type I stable structure (cubic) is studied for structural, elastic, mechanical and vibrational properties by using Density Functional Theory (DFT). Three independent elastic constants [Formula: see text], [Formula: see text] and [Formula: see text] for this cubic system are computed with Generalized Gradient Approximation (GGA) functional. The mechanical parameters like Young’s modulus, Shear and Bulk modulus, Pugh’s ratio, Poisson’s ratio, anisotropic factor, Cauchy pressure are then calculated by using these cubic elastic parameters. In addition, phonon dispersion curve and phonon density of states (PDOS) are computed with norm-conserving Martins–Troullier pseudo-potential in Perturbed Density Functional Theory. The phonon dispersion curve provides reststrahlen band 0.727 THz [Formula: see text] for which material behaves as 100%. This value corresponds to Far Infra-Red (FIR) spectral region so this alloy can be used for manufacturing FIR-devices.

scholarly journals Transferability of Molecular Potentials for 2D Molybdenum Disulphide

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 519
Author(s):  
Marcin Maździarz
Keyword(s):  
Mechanical Properties ◽  
Density Functional Theory ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Single Layer ◽  
Interatomic Potentials ◽  
Molybdenum Disulphide ◽  
Functional Theory ◽  
Systematic Comparison ◽  
Molecular Potentials

An ability of different molecular potentials to reproduce the properties of 2D molybdenum disulphide polymorphs is examined. Structural and mechanical properties, as well as phonon dispersion of the 1H, 1T and 1T’ single-layer MoS2 (SL MoS2) phases, were obtained using density functional theory (DFT) and molecular statics calculations (MS) with Stillinger-Weber, REBO, SNAP and ReaxFF interatomic potentials. Quantitative systematic comparison and discussion of the results obtained are reported.

Electronic Structure and Half-Metallic Properties of Cubic Perovskite BaRu1-XTixO3 System

2012 ◽  
Vol 519 ◽  
pp. 174-178
Author(s):  
Tong Wei Li ◽  
La Chen ◽  
Yang Wang ◽  
Jin Cang Zhang
Keyword(s):  
Density Functional Theory ◽  
Electronic Structures ◽  
Density Functional ◽  
Energy Gap ◽  
Metallic Phase ◽  
Wave Method ◽  
Functional Theory ◽  
Half Metallic ◽  
Plane Wave Method ◽  
Spin Polarized

The electronic structures of the titanium-doped cubic perovskite ruthenates BaRu1-xTixO3 with x=0.125, 0.25, 0.375, 0.5, 0.625, 0.75, and 0.875 are investigated using the spin-polarized density functional theory within the pseudopotential plane wave method. It is found that a half-metallic phase appears in the 0.75- and 0.875-doped systems, and the origin of half-metallic property is the decrease of t2g bandwidth of Ru 4d states with the increase in x. In addition, the energy gap of BaRu0.25Ti0.75O3 is as large as 1.7 eV at the Fermi level in the up-spin density of states, which suggests a stable half-metallic phase can be obtained in the present systems.

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