A First Principles Study of Thermal Properties of Yb-Pnictides (YbX, X= N, P and As) Compounds

2013 ◽  
Vol 665 ◽  
pp. 353-358
Author(s):  
Himadri R. Soni ◽  
Prafulla K. Jha
Keyword(s):  
Free Energy ◽  
Thermal Properties ◽  
Specific Heat ◽  
Internal Energy ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Constant Volume ◽  
Generalized Gradient ◽  
Lattice Specific Heat

Using first principles density functional theoretical calculations within the generalized gradient approximation (GGA), the present paper reports thermal properties such as constant volume lattice specific heat, Gibbs free energy, internal energy, and entropy of Yb-pnictides such as YbN, YbP and YbAs in its rocksalt phase. The variation of lattice specific heat with temperature obeys the classical Dulong-Petits law at high temperature while at low temperature it obeys Debye T3 law. The internal energy, entropy and free energy show a gradual variation with temperature. The specific heat at constant volume at lower temperature increases as going from N to P to As. *Corresponding author Email: [email protected], [email protected] Telephone: +91-278-2422650 Fax: +91-278-2426706

First-Principles Studies of the Magnetic Properties of hcp Cr in Cr/Cu(111) and Cr/Ru(0001) Superlattices

2002 ◽  
Vol 721 ◽  
Author(s):  
G. Y. Guo
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Recent Observation ◽  
Theoretical Calculations ◽  
Ferromagnetic State ◽  
Full Potential ◽  
Generalized Gradient ◽  
Plane Wave Method ◽  
Wide Range ◽  
Linearized Augmented Plane Wave

AbstractLatest first-principles density functional theoretical calculations using the generalized gradient approximation and highly accurate all-eleectron full-potential linearized augmented plane wave method, show that bulk hcp Cr would be a paramagnet and that no ferromagnetic state could be stabilized over a wide range of volume [1]. To understand the recent observation of the weakly ferromagnetic state of Cr in hcp Cr/Ru (0001) superlattices [2], the same theoretical calculations have been carried out for the hcp Cr3/Ru7 (0001) and hcp Cr3/fcc Cu6 (111) superlattices. The Cr/Ru superlattice is found to be ferromagnetic with a small magnetic moment of ∼0.31μB/Cr while in contrast, Cr/Cu superlattice is found to be nonmagnetic.

Ab initio study of thermodynamic properties of bulk zinc-blende CdS: Comparing the LDA and GGA

2018 ◽  
Vol 32 (20) ◽  
pp. 1850207 ◽  
Author(s):  
Fatemeh Badieian Baghsiyahi ◽  
Arsalan Akhtar ◽  
Mahboubeh Yeganeh
Keyword(s):  
Free Energy ◽  
Thermal Expansion ◽  
Thermodynamic Properties ◽  
Bulk Modulus ◽  
Internal Energy ◽  
Density Functional ◽  
Helmholtz Free Energy ◽  
Constant Volume ◽  
Grüneisen Parameter ◽  
Zinc Blende

In the present study, we have investigated the phonon and thermodynamic properties of bulk zinc-blende CdS by first-principle calculations within the density functional theory (DFT) and the density functional perturbation theory (DFPT) method using the quasi harmonic approximation (QHA). We calculated the phonon dispersion at several high symmetry directions, density of phonon state, temperature dependence feature of Helmholtz free energy (F), internal energy, bulk modulus, constant-volume specific heat, entropy, coefficient of the volume thermal expansion and Grüneisen parameter estimated with the local density approximation (LDA) and generalized gradient approximation (GGA) for the exchange-correlation potential and compared them with each other. For internal energy, Helmholtz free energy, constant volume heat capacity and phonon entropy the LDA and GGA results are very similar. But, the LDA gives lattice constants that are smaller than GGA while phonon frequencies, bulk modulus and cohesive energies are larger. On the other hand, the results obtained through the GGA approximation for the coefficient of the volume thermal expansion and Grüneisen parameter are larger than those obtained from LDA.

Ab Initio Study of the Phonon Frequency, Electrical and Thermal Properties of TiN

2012 ◽  
Vol 155-156 ◽  
pp. 291-297
Author(s):  
Xin Tan ◽  
Yu Qing Li ◽  
Xue Jie Liu
Keyword(s):  
Electronic Structure ◽  
Thermal Properties ◽  
Specific Heat ◽  
Density Functional ◽  
Correlation Energy ◽  
Phonon Dispersion ◽  
Harmonic Approximation ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Phonon Spectra

With a motivation to understand microscopic aspects of TiN relevant to the electronic structure, phonon and thermal properties of transition metal nitride TiN superlattices, we determine its electronic structure, phonon spectra and thermal properties using first-principles calculations based on density functional theory with a generalized gradient approximation of the exchange correlation energy. We find that the electronic bands crossed by EF are half occupied, TiN has the ability of taking part in chemical reactions and also has the surface activity; A large gap in its phonon spectra, anomalies in the phonon dispersion of metallic TiN, manifested as dips in acoustic branches, but it do not contain soft modes in any direction; The specific heat (Cv) of TiN rises rapidly at low temperatures, the Cv values of the material, is identical to the Dulong-Petit value at high temperatures. Under the quasi-harmonic approximation (QHA), the thermal expansion, specific heat and bulk modulus B(T) are obtained, and the B(T) decreases along with the increase of temperature.

Lattice dynamics, phonon vibrational spectra, and thermal properties of tetragonal SrPt3P: a first-principles study

RSC Advances ◽  
2016 ◽  
Vol 6 (32) ◽  
pp. 27060-27067 ◽  
Author(s):  
Xiu-Qing Zhang ◽  
Zhao-Yi Zeng ◽  
Yan Cheng ◽  
Guang-Fu Ji
Keyword(s):  
Density Functional Theory ◽  
Thermal Properties ◽  
Vibrational Spectra ◽  
First Principles ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
First Principles Study

The phonon vibrational spectra and thermal properties of the platinum-based superconductor SrPt3P are investigated by the generalized gradient approximation (GGA) in the framework of density functional theory (DFT).

Theoretical investigations on elastic, thermal and lattice dynamic properties of chalcopyrite ZnSnX2 (X = P, As, Sb) under pressure and temperature: The first-principles calculation

2018 ◽  
Vol 32 (30) ◽  
pp. 1850329 ◽  
Author(s):  
Hui Liu ◽  
Beijun Zhao ◽  
You Yu ◽  
Zhiyu He ◽  
Jianping Xiao ◽  
...  
Keyword(s):  
Thermal Properties ◽  
First Principles ◽  
Density Functional ◽  
Dynamic Properties ◽  
Infrared Absorption Spectrum ◽  
Empirical Relation ◽  
Debye Model ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Reported Data

We performed the first-principles calculations on the elastic and thermal properties for chalcopyrite ZnSnX2 (X = P, As, Sb), employing the ultrasoft pseudo-potentials and generalized gradient approximation (GGA) under the frame of density functional theory. The equilibrium structural lattice constants are in good agreement with reported data. The elastic characteristics were evaluated under high-pressure condition (0–20 GPa), such as the elastic constants, bulk modulus, shear modulus, Poisson’s ratio, Zener anisotropy and compressibility index. Combining with quasi-harmonic Debye model, the thermal properties were confirmed at different temperatures (0–1200 K) and pressures (0–20 GPa), including the heat capacity, thermal expansion, Debye temperature, entropy, and Grüneisen parameter. Based on the semi-empirical relation, the hardness of materials was determined at various temperatures and pressures. Finally, the phonon spectrum curves and vibration frequencies of phonon were evaluated to confirm the thermodynamic stability of ZnSnX2. The Raman scattering spectrum and infrared absorption spectrum were simulated for chalcopyrite ZnSnX2.

scholarly journals Free Energy of Metals from Quasi-Harmonic Models of Thermal Disorder

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 195
Author(s):  
Pavel A. Korzhavyi ◽  
Jing Zhang
Keyword(s):  
Free Energy ◽  
First Principles ◽  
Density Functional ◽  
Helmholtz Free Energy ◽  
Complex Materials ◽  
Predictive Capability ◽  
Temperature Dependent ◽  
Disordered Alloys ◽  
Thermal Disorder ◽  
Structure Calculations

A simple modeling method to extend first-principles electronic structure calculations to finite temperatures is presented. The method is applicable to crystalline solids exhibiting complex thermal disorder and employs quasi-harmonic models to represent the vibrational and magnetic free energy contributions. The main outcome is the Helmholtz free energy, calculated as a function of volume and temperature, from which the other related thermophysical properties (such as temperature-dependent lattice and elastic constants) can be derived. Our test calculations for Fe, Ni, Ti, and W metals in the paramagnetic state at temperatures of up to 1600 K show that the predictive capability of the quasi-harmonic modeling approach is mainly limited by the electron density functional approximation used and, in the second place, by the neglect of higher-order anharmonic effects. The developed methodology is equally applicable to disordered alloys and ordered compounds and can therefore be useful in modeling realistically complex materials.

Structural, elastic and thermodynamic properties of A15-type compounds V3X (X = Ir, Pt and Au) from first-principles calculations

2016 ◽  
Vol 30 (35) ◽  
pp. 1650414 ◽  
Author(s):  
Mingliang Wang ◽  
Zhe Chen ◽  
Dong Chen ◽  
Cunjuan Xia ◽  
Yi Wu
Keyword(s):  
Thermodynamic Properties ◽  
Debye Temperature ◽  
First Principles ◽  
Density Functional ◽  
Coefficient Of Thermal Expansion ◽  
Local Density ◽  
Debye Model ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Experimental Values

The structural, elastic and thermodynamic properties of the A15 structure V3Ir, V3Pt and V3Au were studied using first-principles calculations based on the density functional theory (DFT) within generalized gradient approximation (GGA) and local density approximation (LDA) methods. The results have shown that both GGA and LDA methods can process the structural optimization in good agreement with the available experimental parameters in the compounds. Furthermore, the elastic properties and Debye temperatures estimated by LDA method are typically larger than the GGA methods. However, the GGA methods can make better prediction with the experimental values of Debye temperature in V3Ir, V3Pt and V3Au, signifying the precision of the calculating work. Based on the E–V data derived from the GGA method, the variations of the Debye temperature, coefficient of thermal expansion and heat capacity under pressure ranging from 0 GPa to 50 GPa and at temperature ranging from 0 K to 1500 K were obtained and analyzed for all compounds using the quasi-harmonic Debye model.

Electronic structure of cubic BaTbO3 from first-principles pseudopotential calculations

2006 ◽  
Vol 84 (2) ◽  
pp. 115-120 ◽  
Author(s):  
G Y Gao ◽  
K L Yao ◽  
Z L Liu
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Pseudopotential Calculations ◽  
Correlation Potential ◽  
Density Contour

First-principles calculations of the electronic structure are performed for cubic BaTbO3 using the plane-wave pseudopotential method within the framework of density functional theory and using the generalized gradient approximation for the exchange-correlation potential. Our calculations show that cubic BaTbO3 is metallic, and that this metallic character is mainly governed by the Tb 4f electrons and the hybridization between the Tb 5d and O 2p states. From the analysis of the density of states, band structure, and charge density contour, we find that the chemical bonding between Tb and O is covalent while that between Ba and TbO3 is ionic. PACS Nos.: 71.15.Mb, 71.20.-b

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