FIRST PRINCIPLES STUDY OF BORON SEGREGATION ON THE ${\rm Si}(111)(\sqrt{3} \times \sqrt{3}){\rm R}30^{\circ}$ SURFACE

2009 ◽  
Vol 16 (02) ◽  
pp. 167-170 ◽  
Author(s):  
V. G. ZAVODINSKY ◽  
E. N. CHUKUROV ◽  
I. A. KUYANOV
Keyword(s):  
Plane Wave ◽  
First Principles ◽  
Local Density Approximation ◽  
Local Density ◽  
Experimental Studies ◽  
Basis Set ◽  
Published Data ◽  
Density Approximation ◽  
Segregation Energy ◽  
Boron Segregation

Segregation of boron on [Formula: see text] surface has been studied using the periodical calculations within the local density approximation. The obtained segregation energy (enthalpy) of about -1.9 eV is close to the published data of experimental studies and previous cluster semiempirical calculations. The influence of plane-wave basis set cutoff energy and the slab unit cell depth on the value of segregation energy has been investigated.

OPTICAL PROPERTIES OF THE CUBIC AlxGa1-xN ALLOY

2013 ◽  
Vol 27 (17) ◽  
pp. 1350127
Author(s):  
S. HADJI ◽  
S. BERRAH ◽  
H. ABID
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Plane Wave ◽  
Absorption Coefficient ◽  
Local Density Approximation ◽  
Local Density ◽  
Full Potential ◽  
Density Approximation ◽  
Augmented Plane Wave ◽  
Coefficient Versus

In this paper, we present numerical calculations based on the full potential augmented plane wave (FP-LAPW) method within the local density approximation (LDA) to study the optical properties of the ternary alloy Al x Ga 1-x N . The shape of the dielectric function, the refractive index, and the absorption coefficient versus photon energy were presented. From the results, we deduce the possibility of this alloy to be used in the optoelectronic and photovololtaic area.

scholarly journals Thermodynamic properties, electronic and crystallographic structure, and magnetic response of the Sr2HoNbO6 material

2018 ◽  
Vol 42 (164) ◽  
pp. 180
Author(s):  
Críspulo E. Deluque Toro ◽  
Ariday S. Mosquera Polo ◽  
Jorge I. Villa Hernández ◽  
David Arsenio Landínez Téllez ◽  
Jairo Roa-Rojas
Keyword(s):  
Thermodynamic Properties ◽  
Plane Wave ◽  
Local Density Approximation ◽  
Local Density ◽  
Crystallographic Structure ◽  
Magnetic Response ◽  
Full Potential ◽  
Density Approximation ◽  
Augmented Plane Wave ◽  
Linearized Augmented Plane Wave

En el presente trabajo se utilizó el código Wien2k, en el marco de la teoría del funcional de la densidad de Kohn-Sham, aplicando el método de ondas planas aumentadas y linealizadas (full-potential linearized augmented plane wave, FP- LAPW) y adoptando la aproximación de gradiente generalizado (GGA) de Perdew, Burke y Ernzerhof para la energía de intercambio y correlación, así como la aproximación de densidad local (local density approximation, LDA) para el cálculo de la densidad de estados y la estructura de bandas de la perovskita doble Sr2HoNbO6. Para los cálculos se consideró el grupo Fmm (#225), experimentalmente obtenido a partir de mediciones de difracción de rayos X y del método de refinamiento de Rietveld. El parámetro de red experimental fue de 8.018 Å, el cual concuerda en un 99,2 % con las predicciones teóricas efectuadas a partir de la minimización de la energía mediante la ecuación de estado de Murnaghan. A partir de mediciones de susceptibilidad magnética en función de la temperatura y del ajuste con la ley de Curie, se obtuvo el valor del momento magnético efectivo 10,01 μB. Este valor es muy cercano del esperado teóricamente a partir de las reglas de Hund (10,60 μB). La brecha de energía determinada entre las bandas de valencia y de conducción fue de 3,3 eV, lo que revela el carácter aislante de la perovskita compleja Sr2HoNbO6 para la configuración de espín hacia arriba, en tanto que se observó el carácter semiconductor para la polarización de espín hacia abajo, con una brecha de energía de 0,77 eV. Las propiedades termodinámicas se calcularon a partir de la ecuación de estado usando el modelo cuasi-armónico de Debye. Un comportamiento del calor específico, con CV≈CP, se encontró a temperaturas inferiores a T = 500 K, con valores del límite de Dulong-Petit que doblaban los que se han reportado para materiales del tipo de la perovskita. © 2018. Acad. Colomb. Cienc. Ex. Fis. Nat.

Possible Ferroelectricity in SnTiO3 by First-Principles Calculations

2002 ◽  
Vol 748 ◽  
Author(s):  
Yoshinori Konishi ◽  
Michio Ohsawa ◽  
Yoshiyuki Yonezawa ◽  
Yoshiya Tanimura ◽  
Toyohiro Chikyow ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Spontaneous Polarization ◽  
First Principles ◽  
Local Density Approximation ◽  
Lattice Structure ◽  
Local Density ◽  
Density Approximation ◽  
First Principles Calculations ◽  
Minimum Total Energy ◽  
The Moment

ABSTRACTThe prospect of lattice structure and ferroelectricity of SnTiO3 have been studied by first-principles calculations within local density approximation. The results showed that the SnTiO3 has the minimum total energy within almost tetragonal perovskite structure of a=b=3.80 Å, c=4.09 Å. The calculated electronic structure of SnTiO3 resembles that of PbTiO3 because the Ti 3d states, Sn 5s and 5p states hybridize with the O 2p orbitals. The moment of spontaneous polarization of SnTiO3 was estimated as 73 μ C/cm2, which is as large as that of PbTiO3.

First-Principles Investigation of ThO2

2012 ◽  
Vol 535-537 ◽  
pp. 2531-2534 ◽  
Author(s):  
Ya Ping Li ◽  
Ping Qian ◽  
Li Jun Bai ◽  
Jin Chun Li ◽  
Jiang Shen
Keyword(s):  
Experimental Data ◽  
First Principles ◽  
Energy Band ◽  
Local Density Approximation ◽  
Local Density ◽  
Lattice Parameter ◽  
Density Approximation ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Densities Of States

We systematically performed first-principles investigations of the structural properties, electron energy band, and densities of states (DOS) for ThO2. All calculations were carried out using the local density approximation (LDA), generalized gradient approximation (GGA), LDA+U, and GGA+U approaches. We also compared our findings with experimental data and other calculations. The lattice parameter obtained using the GGA+U agrees well with the experimental value.

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