Relative stability and phase transitions under pressure of SrTiO3: ab initio FP-LAPW within GGA-PBEsol+TB-mBJ calculations

2014 ◽  
Vol 28 (19) ◽  
pp. 1450121 ◽  
Author(s):  
Yassine Benallou ◽  
Belabbas Soudini ◽  
Kadda Amara
Keyword(s):  
Phase Transitions ◽  
Relative Stability ◽  
Density Functional ◽  
Solid Phase ◽  
Theoretical Calculations ◽  
Structural Parameters ◽  
Functional Study ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative

In this paper, we report a density functional study of the structural, electronic and pressure-induced solid–solid phase transitions of SrTiO 3. These first-principles calculations have been performed using the full potential linearized augmented plane wave method (FP-LAPW) within the generalized gradient approximation (GGA) developed by Perdew–Burke–Ernzerhor for solids (PBEsol). The calculated structural parameters like the lattice parameters, the bulk modulus B and their pressure derivative B ′ are used to analyze the relative stability and phase transitions under pressure of SrTiO 3. Calculations were done for the cubic (Pm-3m), tetragonal (I4/mcm, P4/mbm, P4mm) and orthorhombic (Cmcm, Pnma) structures where we found that the tetragonal I4/mcm phase is the most stable structure compared to the other structures at T = 0 K and P = 0 GPa. For the electronic properties calculations, the exchange and correlation effects were treated by the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential to prevent the shortcoming of the underestimation of the energy gaps in both LDA and GGA approximations. The obtained results are compared to available experimental data and to other theoretical calculations.

Density Functional Study of the Structural Properties of Copper Iodide: LDA vs GGA Calculations

2009 ◽  
Vol 5 ◽  
pp. 25-30 ◽  
Author(s):  
Heribert Hernández-Cocoletzi ◽  
Gregorio H. Cocoletzi ◽  
J.F. Rivas-Silva ◽  
A. Flores ◽  
Noboru Takeuchi
Keyword(s):  
Structural Properties ◽  
Ground State ◽  
Density Functional ◽  
Local Density ◽  
Structural Parameters ◽  
External Pressure ◽  
Functional Study ◽  
Full Potential ◽  
Copper Iodide ◽  
Generalized Gradient

We have performed first principles total energy calculations to investigate the structural properties of copper iodide (CuI) in its sodium chloride, cesium chloride, zincblende and wurtzite structures. Calculations are done using the density functional theory. We employ the full potential linearized augmented plane wave method as implemented in the wien2k code. The exchange and correlation potential energies are treated in the generalized gradient approximation (GGA), and the local density approximation (LDA). Optical absorption experiments and x-ray diffraction measurements have shown that zincblende is the ground state of CuI. Our calculations find that in the GGA formalism wurtzite and zincblende have similar total energies, while in the LDA formalism the lowest minimum corresponds to zincblende. Results show that the energy difference between the wurtzite and the zincblende structures, as calculated within the GGA formalism is 2 meV, and within the LDA formalism, is 31 meV. These results may suggest a coexistence of both wurtzite and zincblende structures in the ground state of CuI. Structural parameters are correctly reproduced by the GGA calculations. We obtain that under the application of external pressure the atomic configuration may transform into the NaCl structure. At higher pressures it is possible to have a phase transition to the CsCl geometry.

Density functional study of the structural and phase transition of silver halides: LDA versus GGA calculations

2019 ◽  
Vol 08 (02) ◽  
pp. 1950006 ◽  
Author(s):  
H. Rekab Djabri ◽  
R. Yagoub ◽  
S. Bahlouli ◽  
S. Amari ◽  
S. Louhibi Fasla
Keyword(s):  
Phase Transition ◽  
Density Functional ◽  
Local Density ◽  
Structural Phase ◽  
Lattice Parameter ◽  
Functional Study ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Structural And Electronic Properties

This paper deals with the theoretical calculation of structural and electronic, properties of AgBr and AgCl compounds using density functional theory within generalized-gradient (GGA) approximation and local density approximation (LDA). We employ the full potential linear muffin-tin orbitals (FP-LMTO) as implemented in the Lmtart code. We have used to examine structure parameter in eight different structures such as in NaCl (B1), CsCl (B2), ZB (B3), NiAs (B8), PbO (B10), Wurtzite (B4), HCP (A3) [Formula: see text]Sn (A5) structures. The equilibrium lattice parameter, bulk modulus and its pressure derivative were presented for all calculated phases. The calculated ground state properties are in good agreement with available experimental and theoretical results. A pressure induced structural phase transition from NaCl (B1) to HCP (A3) phases at 37.66 and 18.11[Formula: see text]GPa for AgBr and AgCl, respectively, and from NaCl to CsCl phase in AgBr and AgCl at 90.55 and 24.4[Formula: see text]GPa, respectively, is also predicted. Furthermore, the band structures are computed. Our results are compared to other theoretical and experimental works, and excellent agreement is obtained.

First principles calculations of structural, electronic and optical properties of InN compound

2015 ◽  
Vol 29 (05) ◽  
pp. 1550028 ◽  
Author(s):  
R. Graine ◽  
R. Chemam ◽  
F. Z. Gasmi ◽  
R. Nouri ◽  
H. Meradji ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Local Density ◽  
Indium Nitride ◽  
Alternative Form ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Electronic And Optical Properties

We carried out ab initio calculations of structural, electronic and optical properties of Indium nitride ( InN ) compound in both zinc blende and wurtzite phases, using the full-potential linearized augmented plane wave method (FP-LAPW), within the framework of density functional theory (DFT). For the exchange and correlation potential, local density approximation (LDA) and generalized gradient approximation (GGA) were used. Moreover, the alternative form of GGA proposed by Engel and Vosko (EV-GGA) and modified Becke–Johnson schemes (mBJ) were also applied for band structure calculations. Ground state properties such as lattice parameter, bulk modulus and its pressure derivative are calculated. Results obtained for band structure of these compounds have been compared with experimental results as well as other first principle computations. Our results show good agreement with the available data. The calculated band structure shows a direct band gap Γ → Γ. In the optical properties section, several optical quantities are investigated; in particular we have deduced the interband transitions from the imaginary part of the dielectric function.

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.

A density functional study of Rh13

2013 ◽  
Vol 91 (7) ◽  
pp. 591-597 ◽  
Author(s):  
Patrizia Calaminici ◽  
José M. Vásquez-Pérez ◽  
Diego A. Espíndola Velasco
Keyword(s):  
Molecular Dynamics ◽  
Ground State ◽  
Density Functional ◽  
Local Density ◽  
Structural Parameters ◽  
Functional Study ◽  
Ground State Structure ◽  
State Structure ◽  
Generalized Gradient ◽  
Density Functional Study

A density functional study was performed for the Rh13 cluster using the linear combination of Gaussian-type orbitals density functional theory (LCGTO-DFT) approach. The calculations employed both the local density approximation (LDA) as well as the generalized gradient approximation (GGA) in combination with a quasi-relativistic effective core potential (QECP). Initial structures for the geometry optimization were taken along Born–Oppenheimer molecular dynamics (BOMD) trajectories. The BOMD trajectories were performed at different temperatures and considered different potential energy surfaces (PES). As a result, several hundred isomers of the Rh13 cluster in different spin multiplicities were optimized with the aim to determine the lowest energy structures. All geometry optimizations were performed without any symmetry restriction. A vibrational analysis was performed to characterize these isomers. Structural parameters, relative stability energy, harmonic frequencies, binding energy, and most relevant Kohn–Sham (KS) molecular orbitals are reported. The obtained results are compared with available data from the literature. This study predicts a low symmetry biplanarlike structure as the ground-state structure of Rh13 with 11 unpaired electrons. This isomer was first noticed by inspection of first-principle Born–Oppenheimer molecular dynamics (BOMD) simulations between 300 and 600 K. This represents the most extensive theoretical study on the ground-state structure of the Rh13 cluster and underlines the importance of BOMD simulations to fully explore the PES landscapes of complicated systems.

First-Principles Calculations of the Structural, Electronic, Optical and Mechanical Properties of CdS, CdSe and CdTe

2013 ◽  
Vol 665 ◽  
pp. 302-306 ◽  
Author(s):  
Sheetal Sharma ◽  
Ajay Singh Verma
Keyword(s):  
Experimental Data ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Zinc Blende ◽  
Optical And Mechanical Properties ◽  
Good Agreement

The structural, electronic, optical and elastic properties of zinc-blende compounds (CdX, X = S, Se and Te), were studied using full-potential augmented plane wave plus local orbitals method (FP-LAPW+ lo) within density functional theory, using generalized gradient approximation (GGA). Geometrical optimization of the unit cell (lattice constant, bulk modulus and its pressure derivative) is in good agreement with experimental data. Results for band structures, density of states, and elastic constants (C11, C12 and C44) are presented. We also report our results on optical properties like the complex dielectric functions and the refractive index (n) of these compounds. Our results are in reasonable agreement with the available theoretical and experimental data.

Structural, Electronic and Elastic Properties of CeTl Intermetallic Compound

2016 ◽  
Vol 28 ◽  
pp. 1-4
Author(s):  
Deepika Shrivastava ◽  
Sankar P. Sanyal
Keyword(s):  
Bulk Modulus ◽  
Elastic Properties ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Cscl Type ◽  
Linearized Augmented Plane Wave

The structural, electronic and elastic properties of CeTl with CsCl-type B2 structure have been investigated using full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT) within the generalized gradient approximation (GGA) for exchange and correlation potential. The ground state properties such as lattice constant, bulk modulus and pressure derivative of bulk modulus have been calculated which are in good agreement with available experimental data. The band structure and density of state depict that 4f electrons of Ce element have dominant character in electronic conduction and are responsible for metallic character of CeTl. The charge density plot reveals that the metallic as well as ionic bonding exist between Ce and Tl atoms. The calculated elastic constants indicate that CeTl is mechanically stable in cubic B2 phase and found to be ductile in nature.

First principle investigations of the optical properties of Zn1-xMgxS, Zn1-xMgxSe and Zn1-xMgxTe ternary alloys

2014 ◽  
Vol 28 (31) ◽  
pp. 1450221 ◽  
Author(s):  
M. Dadsetani ◽  
A. Zeinivand
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Random Phase ◽  
Ternary Alloys ◽  
Optical Absorption Coefficient ◽  
Full Potential ◽  
Generalized Gradient ◽  
The Density Functional Theory ◽  
Ternary Semiconductor

Optical properties of Zn 1-x Mg x S , Zn 1-x Mg x Se and Zn 1-x Mg x Te (0 ≤ x ≤ 1) ternary semiconductor alloys are calculated using the full potential linearized augmented plane wave within the density functional theory. The exchange correlation potential is treated by the generalized gradient approximation (GGA) within Perdew et al. scheme. The real and imaginary parts of the dielectric function ε(ω), the refractive index n(ω), the extinction coefficient k(ω), the optical absorption coefficient α(ω), the reflectivity R(ω) and the electron energy loss function (EELS) are calculated within random phase approximation (RPA). Our results are compared with the previous theoretical calculations and available experimental data. Moreover, the interband transitions responsible for the structures seen in the spectra are specified. It is shown that, the chalcogen p states as initial and Zn 4s, Mg 3s, chalcogen d states as final states perform the major role in optical transitions.

A Density Functional Study of Structure and Stability of Ni8, Ni8 + and Ni8 − Cluster

2005 ◽  
Vol 1 (4) ◽  
pp. 172-182 ◽  
Author(s):  
Patrizia Calaminici ◽  
Marcela R. Beltrán
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Structural Parameters ◽  
Binding Energies ◽  
Functional Study ◽  
Generalized Gradient ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
The Stability ◽  
Anionic Cluster

Density functional calculations of neutral, cationic and anionic nickel octamer are presented. The structure optimization and frequency analysis were performed on the local density approximation (LDA) level with the exchange correlation functional by Vosko,Wilk and Nusair (VWN). Improved calculations for the stability were based on the generalized gradient approximation (GGA) where the exchange correlation functional of Perdew and Wang (PW) was used. For neutral, cationic and anionic cluster several isomers and different spin multiplicities were investigated in order to find the lowest structures. Structural parameters, relative energies, binding energies, harmonic frequencies, adiabatic ionization potential and electron affinity will be presented. The calculated values are compared with available experimental data.

Investigation of the structural, electronic, elastic and thermodynamic properties of Curium Monopnictides: An ab initio study

2017 ◽  
Vol 31 (30) ◽  
pp. 1750226 ◽  
Author(s):  
H. Baaziz ◽  
Dj. Guendouz ◽  
Z. Charifi ◽  
S. Akbudak ◽  
G. Uğur ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Bulk Modulus ◽  
Density Functional ◽  
Local Density ◽  
Structural Parameters ◽  
Structural Phase ◽  
Full Potential ◽  
Generalized Gradient ◽  
Metallic Behavior ◽  
Spin Polarized

The structural, electronic, elastic and thermodynamic properties of Curium Monopnictides CmX (X = N, P, As, Sb and Bi) are investigated using first-principles calculations based on the density functional theory (DFT) and full potential linearized augmented plane wave (FP-LAPW) method under ambient condition and high pressure. The exchange-correlation term is treated using two approximations spin-polarized local density approximation (LSDA) and spin-polarized generalized gradient approximation generalized (GGA). The structural parameters such as the equilibrium lattice parameters, bulk modulus and the total energies are calculated in two phases: namely NaCl (B1) and CsCl (B2). The obtained results are compared with the previous theoretical and experimental results. A structural phase transition from B1 phase to B2 phase for Curium pnictides has been obtained. The highest transition pressure is 122 GPa for CmN and the lowest one is 10.0 GPa for CmBi compound. The electronic properties show that these materials exhibit half-metallic behavior in both phases. The magnetic moment is found to be around 7.0 [Formula: see text]B. The mechanical properties of CmX (X = N, P, As, Sb and Bi) are predicted from the calculated elastic constants. Our calculated results are in good agreement with the theoretical results in literature. The effect of pressure and temperature on the thermodynamic properties like the cell volume, bulk modulus and the specific heats C[Formula: see text] and C[Formula: see text], the entropy [Formula: see text] and the Grüneisen parameter [Formula: see text] have been foreseen at expanded pressure and temperature ranges.

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