scholarly journals Performance of the constrained minimization of the total energy in density functional approximations: the electron repulsion density and potential

2018 ◽  
Vol 91 (6) ◽  
Author(s):  
Tom Pitts ◽  
Nikitas I. Gidopoulos ◽  
Nektarios N. Lathiotakis
Keyword(s):  
Total Energy ◽  
Density Functional ◽  
Constrained Minimization ◽  
Electron Repulsion

Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nilanjan Roy ◽  
Sucharita Giri ◽  
Harshit ◽  
Partha P. Jana
Keyword(s):  
Total Energy ◽  
First Principles ◽  
Density Functional ◽  
Structure Type ◽  
Site Preference ◽  
X Ray Diffraction ◽  
Atomic Ordering ◽  
Functional Theory ◽  
The Stability ◽  
Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

scholarly journals Density-functional Based Tight-binding Calculations on Thiophene Polymorphism

VLSI Design ◽  
2001 ◽  
Vol 13 (1-4) ◽  
pp. 393-397
Author(s):  
J. Widany ◽  
G. Daminelli ◽  
A. Di Carlo ◽  
P. Lugli
Keyword(s):  
Total Energy ◽  
Intermolecular Interaction ◽  
Density Functional ◽  
Tight Binding ◽  
Methyl Groups ◽  
Direct Function ◽  
Energy Calculations ◽  
Polymorphic Modifications

Total energy calculations based on a density-functional tight-binding scheme have been performed on polymorphic modifications of various thiophene crystals. The investigated structures include sulphanyl-substituted quater-thiophene and methyl-substituted sexithiophene, in the monoclinic and triclinic modifications. Attention has been focused on the intermolecular interaction between the molecular units. Despite the similarities in the backbone geometries, the strength and nature of intermolecular interaction differs largely in the various polymorphs. Sulphur atoms belonging to the thiophene rings are strongly involved in the interaction. Sulphanyl substituents play an important role, while methyl groups do not contribute. The strength of intermolecular interaction is not a direct function of atom distance.

Structural and Electronic Properties of Oxygen Vacancies in Monoclinic HfO2

2007 ◽  
Vol 996 ◽  
Author(s):  
Peter Broqvist ◽  
Alfredo Pasquarello
Keyword(s):  
Oxygen Vacancy ◽  
Optical Absorption ◽  
Total Energy ◽  
Band Gap ◽  
Electronic Properties ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Structural And Electronic Properties ◽  
Defect Levels ◽  
Hybrid Density Functional

AbstractWe study structural and electronic properties of the oxygen vacancy in monoclinic HfO2 for five different charge states. We use a hybrid density functional to accurately reproduce the experimental band gap. To compare with measured defect levels, we determine total-energy differences appropriate to the considered experiments. Our results show that the oxygen vacancy can consistently account for the defect levels observed in optical absorption, direct electron injection, and trap-assisted conduction experiments.

scholarly journals New Ternary Compounds of the Composition Cu2SnTi3 and Their Crystal Structures

2020 ◽  
Vol 10 (24) ◽  
pp. 8776
Author(s):  
Sheng-Fang Huang ◽  
Yen-Cheng Chang ◽  
Po-Liang Liu
Keyword(s):  
Crystal Structure ◽  
Total Energy ◽  
Ternary Compound ◽  
Density Functional ◽  
Hexagonal Crystal Structure ◽  
X Ray Diffraction ◽  
Hexagonal Crystal ◽  
Orthorhombic Crystal Structure ◽  
X Ray ◽  
Atomic Structures

A new ternary compound Cu2SnTi3 has been synthesized by vacuum sintering at 900 °C. The atomic structures of CaCu5- and InNi2-like Cu2SnTi3 are calculated using density functional theory methods. The X-ray diffraction (XRD) analysis and selected area diffraction (SAD) patterns of the new ternary compound Cu2SnTi3 are considered to verify the atomic structures of CaCu5- and InNi2-like Cu2SnTi3. The results reveal that the InNi2-like Cu2SnTi3 model has the lowest total energy of −35.239 eV, representing the trigonal crystal structure. The orthorhombic crystal structure of the CaCu5-like Cu2SnTi3 model has the second lowest total energy of −33.926 eV. Our theoretical X-ray diffraction peak profiles of InNi2-like (CaCu5-like) Cu2SnTi3 are nearly identical to experimental one, leading to an error below 2.0% (3.0%). In addition, the hexagonal crystal structure of the CaCu5-like Cu2SnTi3 model has the highest total energy of −33.094 eV. The stability of the Cu2SnTi3 in terms of energy follows the order: the trigonal, orthorhombic, and hexagonal crystal structure.

The Studies of ScB2 (0001) Surfaces from the First-Principles

2014 ◽  
Vol 989-994 ◽  
pp. 688-693
Author(s):  
Hui Zhao ◽  
Qian Han
Keyword(s):  
Energy Density ◽  
Total Energy ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Surface Structures ◽  
Charge Accumulation ◽  
Total Energy Density ◽  
Energy Density Functional

We conduct first-principles total-energy density functional calculations to study the ScB2 (0001) surfaces. The optimized surface structures and electronic properties are obtained. The results show that Sc-terminated surface is thermodynamically more favorable in most of range. The relaxations indicate that it is mainly localized within top three layers and it is less relaxation for Sc-terminated surface. The surface induced features in DOS disappear slowly for the B-terminated surface but vanish rapidly for the Sc-terminated surface. For the Sc-terminated surface, it shows strong metallic property. Simultaneously, both termination surfaces are found charge accumulation relative to the idea surface. Sc-B bonds are strengthened result in the outermost interface spacing are all contracted.

First-Principles Geometry Optimization of Polysilane

1988 ◽  
Vol 141 ◽  
Author(s):  
John W. Mintmire
Keyword(s):  
Total Energy ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Minimum Energy ◽  
Geometry Optimization ◽  
Functional Approach ◽  
Energy Structure ◽  
Atomic Orbitals ◽  
Local Density Functional

AbstractA first-principles approach is reviewed for calculating the total energy of chain polymers using a linear combination of atomic orbitals local-density functional approach. The geometry for the all-trans conformation of polysilane is optimized by finding the minimum energy structure using this method.

Local Structural Variations in Al72Ni20Co8 Decagonal Quasicrystals

2003 ◽  
Vol 805 ◽  
Author(s):  
Yanfa Yan ◽  
S. J. Pennycook
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Total Energy ◽  
First Principles ◽  
Density Functional ◽  
High Resolution Electron Microscopy ◽  
Structural Variations ◽  
Decagonal Quasicrystals ◽  
Resolution Electron ◽  
Microscopy Images

ABSTRACTWe investigate local structural variations in Al72Ni20Co8 quasicrystals using first principles density-functional total-energy calculations. We find that local chemical fluctuation can cause large structural variations on the central rings of the 2-nm clusters. Such structure variations may result in ambiguities at the central rings in high-resolution electron microscopy images of Al72Ni20Co8 decagonal quasicrystals.

Structural, Electronic, and Magnetic Properties of Surfaces, Interfaces, and Superlattices

1985 ◽  
Vol 63 ◽  
Author(s):  
Arthur J. Freeman ◽  
C. L. Fu ◽  
T. Oguchi
Keyword(s):  
Total Energy ◽  
Density Functional ◽  
Local Density ◽  
Full Potential ◽  
Complex Materials ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Local Density Functional Theory ◽  
Flapw Method ◽  
Linearized Augmented Plane Wave

ABSTRACTAdvances in all-electron local density functional theory approaches to complex materials structure and properties made possible by the implementation of new computational/theoretical algorithms on supercomputers are exemplified in our full potential linearized augmented plane wave (FLAPW) method. In this total energy self-consistent approach, high numerical stability and precision (to 10 in the total energy) have been demonstrated in a study of the relaxation and reconstruction of transition metal surfaces. Here we demonstrate the predictive power of this method for describing the structural, magnetic and electronic properties of several systems (surfaces, overlayers, sandwiches, and superlattices).

ATOMIC STRUCTURE STUDY OF THE Ag/MgO(100) SURFACE BY AN AB INITIO, TOTAL ENERGY MOLECULAR CLUSTER METHOD USING DENSITY FUNCTIONAL THEORY

1996 ◽  
Vol 03 (03) ◽  
pp. 1365-1375 ◽  
Author(s):  
LAURENT SPIESS
Keyword(s):  
Density Functional Theory ◽  
Total Energy ◽  
Ab Initio ◽  
Density Functional ◽  
Structure Study ◽  
Cluster Method ◽  
Molecular Cluster ◽  
Functional Theory ◽  
Molecular Systems ◽  
Coverage Dependence

The clean and Ag-covered MgO(100) surface is investigated by an all-electron, total energy, ab initio DMol molecular method (Density functional theory for Molecular systems). A large cluster of 100 atoms (including 50 oxygen and 50 magnesium) is built to represent the surface. A point charge embedding is used to investigate the electronic properties. The small relaxation of the surface, referred to as rumpling, is exhibited and shown to have barely no effect on the adsorption of Ag on the surface. The oxygen site is found to be the most stable for Ag atom adsorption, in good agreement with previous ab initio theoretical studies. The adsorption of a five-Ag-atom layer on the MgO(100) surface provides new and interesting results concerning the surface coverage dependence. We have used the unique ability of cluster methods to study the structural effects of the 3% mismatch at the Ag/MgO(100) interface, and we show that Ag atoms are likely to grow on the surface without epitaxy at low coverages.

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