FIRST-PRINCIPLES INVESTIGATION OF SnO2 AT HIGH PRESSURE

2005 ◽  
Vol 19 (27) ◽  
pp. 4081-4092 ◽  
Author(s):  
F. EL HAJ HASSAN ◽  
A. ALAEDDINE ◽  
M. ZOAETER ◽  
I. RACHIDI
Keyword(s):  
Total Energy ◽  
Density Functional ◽  
Tin Dioxide ◽  
Correlation Energy ◽  
Structural Phase ◽  
Cubic Phase ◽  
Full Potential ◽  
Generalized Gradient ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation

The ground state properties and the structural phase transformation of tin dioxide ( SnO 2) have been investigated using first principle full potential-linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). We used local density approximation (LDA) and the generalized gradient approximation (GGA), which are based on exchange-correlation energy optimization, to optimize the internal parameters by relaxing the atomic positions in the force directions and to calculate the total energy. For band structure calculations, we utilized both the Engel-Vosko's generalized gradient approximation (EVGGA), which optimizes the exchange-correlation potential, and also GGA. From the obtained band structures, the electron (hole) valance and conduction effective masses are deduced. For compressed volumes SnO 2 is shown to undergo two structural phase transitions with increasing pressure from the rutile- to the CaCl 2-type phase at 12.4 GPa and to a cubic phase, space group [Formula: see text] at 22.1 GPa. The calculated total energy allowed us to investigate several structural properties, in particular, the equilibrium lattice constants, bulk modulus, cohesive energy, interatomic distances and the angles between different atomic bonds. In addition, we discuss the bonding parameter in term of charge density, which show the localization of charge around the anion side.

scholarly journals COMPARISON OF DENSITY FUNCTIONAL APPROXIMATIONS IN THE JELLIUM MODEL FOR METAL CLUSTERS

2001 ◽  
Vol 15 (10n11) ◽  
pp. 1724-1727 ◽  
Author(s):  
CARLOS FIOLHAIS ◽  
L. M. ALMEIDA
Keyword(s):  
Monte Carlo ◽  
Density Functional ◽  
Alkali Metals ◽  
Correlation Energy ◽  
Local Density ◽  
Jellium Model ◽  
Generalized Gradient ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Exchange And Correlation

We calculated the exchange, correlation and total energies of clusters of alkali metals with N=1-150 atoms in the spherical jellium model. The calculations were made using the Kohn-Sham method with exchange and correlation energies evaluated in the meta-generalized gradient approximation (MGGA), proposed by J. P. Perdew, S. Kurth, A. Zupan and P. Blaha, in the generalized gradient approximation (GGA) of J. P. Perdew, K. Burke and M. Ernzerhof, and in the Local Density Approximation (LDA). We evaluated the relative deviations of MGGA and GGA energies with respect to LDA. Exchange energies of MGGA and GGA are more negative than the LDA exchange energy and become closer to this as the cluster size increases. On the other hand, the GGA and MGGA correlation energies, which are almost identical, are less negative than LDA. The deviations of GGA and MGGA exchange-correlation energies with respect to LDA are smaller than those of the exchange and correlation energies separately. For clusters with 18 and 20 atoms we have compared our jellium results with Variational and Diffusion Monte-Carlo results. Errors of LDA for exchange and correlation tend to cancel so that the total exchange-correlation energy is close to the Monte-Carlo results. Similar cancellations occur with GGA and MGGA. We also examined the validity of the liquid drop model.

Effect of Helium on Stabilizing Vacancy Configuration in Delta-Plutonium

2013 ◽  
Vol 750-752 ◽  
pp. 2206-2211
Author(s):  
Guo Xun Ji ◽  
Ru Song Li ◽  
Bin He
Keyword(s):  
Total Energy ◽  
Density Functional ◽  
Radioactive Decay ◽  
First Principle ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Physical Chemical ◽  
The Density Functional Theory

The radioactive decay of Pu produces He atom, which may form cluster with vacancies or accumulate into He bubble, thus resulting in physical, chemical and mechanical changes. In this paper first principle evaluations of Pu lattice defected with mono-vacancy (or di-vacancy) and He atoms have been performed using the generalized gradient approximation (GGA) of the density functional theory and Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional. The simulation results indicate that the density of states (DOSs) of Pu lattices seem stable when He/V (V represents vacancy) ratio is between 2:1-3:1, the partial DOSs of s, d and f states shift in the orientation of positive X axis, while f state peaks disappear around the Fermi level. Total energy per Pu atom in Pu lattice with mono-vacancy (or di-vacancy) and He atoms relative to total energy per Pu atom in perfect fcc Pu lattice nearly remains constant (about 8.18a.u.).

Electronic properties of austenite and martensite Fe-9%Mn alloys

Open Physics ◽  
2008 ◽  
Vol 6 (4) ◽  
Author(s):  
Ercan Uçgun ◽  
Hamza Ocak
Keyword(s):  
Total Energy ◽  
Electronic Properties ◽  
Lattice Relaxation ◽  
The Self ◽  
Full Potential ◽  
Generalized Gradient ◽  
Plane Wave Method ◽  
Lattice Constants ◽  
Generalized Gradient Approximation ◽  
Self Consistent

AbstractWe calculate the electronic properties of austenite and martensite Fe-9%Mn alloys using the self consistent full-potential linearized-plane-wave method under the generalized gradient approximation full lattice relaxation. By minimizing total-energy, the lattice constants in their ground states were determined. We discuss the total energy dependence of the volume, and density of states (DOS).

MAGNETIC MAP OF MnNi ALLOYED MONOLAYER ON Cu(001) SUBSTRATE: AB-INITIO CALCULATIONS

2010 ◽  
Vol 09 (06) ◽  
pp. 619-622
Author(s):  
BOTHINA A. HAMAD
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Magnetic Moments ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Exchange Correlation Potential ◽  
The Density Functional Theory ◽  
Correlation Potential

In this work, a theoretical study of the structural, electronic and magnetic properties are presented for Mn 0.5 Ni 0.5 alloyed overlayer adsorbed on Cu (001) surface. The calculations were performed using the density functional theory (DFT) and the exchange-correlation potential was treated by the generalized gradient approximation (GGA). The system was fully relaxed except for the central layer, which yields to outward relaxations and inward Mn and Ni surface atoms, respectively in the ferromagnetic and antiferromagnetic configurations. The in-plane ferromagnetic configuration was found to be more stable than the antiferromagnetic one by 25 meV/atom. The local magnetic moments of Mn atoms were found to be about 4 μ B , whereas those of the Ni atoms where found to be 0.46 μ B .

EXPLORING THE ADIABATIC CONNECTION BETWEEN WEAK- AND STRONG-INTERACTION LIMITS IN DENSITY FUNCTIONAL THEORY

2001 ◽  
Vol 15 (10n11) ◽  
pp. 1672-1683 ◽  
Author(s):  
JOHN P. PERDEW ◽  
STEFAN KURTH ◽  
MICHAEL SEIDL
Keyword(s):  
Perturbation Theory ◽  
Density Functional ◽  
Correlation Energy ◽  
Interaction Strength ◽  
Kcal Mole ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Density Functional Perturbation Theory ◽  
Simple Interaction

If the electron-electron repulsion in an atom or molecule were very weak, it could be treated by orbital-based perturbation theory. If this repulsion were very strong, it could be treated in a model of strict correlation. A simple interaction strength interpolation between these two limits, at fixed electron density, can describe the reality that lies between the extremes. By working entirely within a sophisticated density functional approximation, the meta-generalized gradient approximation, we find that the interpolation error is only about 0.1% for the exchange-correlation energy and about 4 kcal/mole = 0.17 eV for the atomization energy. We also find that real systems probably lie close to the radius of convergence of density functional perturbation theory.

Density Functional Calculations on Electronic and Magnetic Properties of Fe-Pt Systems

2005 ◽  
Vol 475-479 ◽  
pp. 3103-3106 ◽  
Author(s):  
You Song Gu ◽  
Jian He ◽  
Zhen Ji ◽  
Xiao Yan Zhan ◽  
Yue Zhang ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Moment ◽  
Electronic Structures ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Experimental Values ◽  
Pseudo Potential

The electronic structures and magnetic properties of Fe-Pt systems were calculated by CASTEP codes, which employed density functional theory, generalized gradient approximation (GGA), Perdew Burke Ernzerh exchange correlation, Pulay density-mixing scheme and Ultra Soft pseudo potential. The band structures and density of states (DOS) were calculated, together with band populations and magnetic properties. The calculated results of α-Fe show the validatiy of this method in predication magnetic properties. It is found that as the Pt concentration increases, Fe 4s and 3d electrons decrease while 4p electrons increase, and the magnetic moment of Fe atom increases. Pt atoms also contribute to the magnetic moment due to polarization. The calculated magnetization agrees with experimental values quite well.

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.

scholarly journals Theoretical Prediction of Lanthanum Composition Effects on Structural, Electronic and Thermal Properties of LaxSc1-XN Alloys.

2021 ◽  
Author(s):  
Amira EL-HASSASNA ◽  
CHAOUCHE Yassine ◽  
Louafi Ahd
Keyword(s):  
Thermal Properties ◽  
Density Functional ◽  
Correlation Energy ◽  
Small Deviation ◽  
Debye Model ◽  
Ternary Alloys ◽  
Full Potential ◽  
Generalized Gradient ◽  
Salt Structure ◽  
Binary Compounds

Abstract In this paper we have study the structural, electronic and thermal properties of LaxSc1−xN ternary alloys in rock-salt structure by the use of full potential linearized augmented plane wave (FP-LAPW) method based to the density functional theory (DFT). For calculate the exchange-correlation energy and potential we are used both the Wu-Cohen generalized gradient (WC-GGA) approximation and the modified Becke-Johnson(mBJ).We investigated the fact of composition on lattice parameters, bulk modulus and band gap. The variation of calculated lattice constant with lanthanum composition is almost linear and shows a small deviation of the obtained results from Vegard’s law. The semiconductor nature of binary compounds ScN and LaN was confirmed. Our finding indicates that the LaxSc1−xN alloys are semiconductor with x = 0.5 and 0.75, on the contrary for x = 0.25 has a metallic nature. Lastly, the effect of thermal macroscopic properties is also investigated employing the quasi-harmonic Debye model in which the lattice vibrations are taken into account. We have found a good accord between our results and the experimental data and previous theoretical results available in the literature for the binary compounds which can be a support for the ternary alloys in the future.

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