scholarly journals Electronic topological transitions and mechanical properties of hafnium dioxide allotrope at high pressure: Evolutionary first-principles techniques

2021 ◽  
Author(s):  
Thipok Bovornratanaraks ◽  
Rajeev Ahuja ◽  
Prutthipong Tsuppayakorn-aek
Keyword(s):  
Mechanical Properties ◽  
Density Functional Theory ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Energy Gap ◽  
Hafnium Dioxide ◽  
Functional Theory ◽  
Topological Transition ◽  
Relative Enthalpy

Abstract Allotrope of HfO2 is explored by using first-principles evolutionary algorithm technique, based on density functional theory. The tetragonal structure with a space group of P4/nmm is found to be thermodynamically stable within the harmonic level. Arising particularly from the relative enthalpy, hafnium dioxide allotrope is taken into account in appraising the dynamic stability. Following this, the phonon calculations display that hafnium dioxide allotrope is dynamically stable under compressed conditions. Along with, the density of states suggests that hafnium dioxide allotrope is demonstrated that it is a semiconductor. Besides, the more significant change in the shape of density of states is observed when the pressure increased, by adopting an effect of this electronic topological transition, resulting in the energy gap is falling down monotonically. By inspecting their elastic constants and Vicker's hardness, the P4/nmm structure displayed the Vicker's hardness of 26.1GPa at a pressure of 200GPa. These findings suggest HfO2 is more likely to be attained experimentally and theoretically in the metal oxides family.

First-principles study of phase stability, electronic and mechanical properties of plutonium sub-oxides

2019 ◽  
Vol 21 (30) ◽  
pp. 16818-16829 ◽  
Author(s):  
P. S. Ghosh ◽  
A. Arya
Keyword(s):  
Mechanical Properties ◽  
Density Functional Theory ◽  
Phase Stability ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
First Principles Study ◽  
Hubbard Parameter ◽  
Formation Energies

Formation energies of PuO2, α-Pu2O3 and sub-oxides PuO2−x (0.0 < x < 0.5) are determined using density functional theory employing generalised gradient approximation corrected with an effective Hubbard parameter.

A STUDY ON STRAIN AFFECTING ELECTRONIC STRUCTURE OF WURTZITE ZnO BY FIRST PRINCIPLES

2009 ◽  
Vol 23 (19) ◽  
pp. 2339-2352 ◽  
Author(s):  
LI BIN SHI ◽  
SHUANG CHENG ◽  
RONG BING LI ◽  
LI KANG ◽  
JIAN WEI JIN ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Band Structure ◽  
Valence Band ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Electron Density Difference ◽  
Different Strains

Density of states and band structure of wurtzite ZnO are calculated by the CASTEP program based on density functional theory and plane-wave pseudopotential method. The calculations are carried out in axial and unaxial strains, respectively. The results of density of states in different strains show that the bottom of the conduction band is always dominated by Zn 4s, and the top of valence band is always dominated by O 2p. The variation of the band gap calculated from band structure is also discussed. In addition, p-d repulsion is used in investigating the variation of the top of the valence band in different strains and the results can be verified by electron density difference.

A MOLECULAR DIODE BASED ON CONJUGATED CO-OLIGOMERS

2006 ◽  
Vol 05 (04n05) ◽  
pp. 535-540
Author(s):  
PING BAI ◽  
CHEE CHING CHONG ◽  
ER PING LI ◽  
ZHIKUAN CHEN
Keyword(s):  
Density Functional Theory ◽  
Spatial Orientation ◽  
First Principles ◽  
Density Functional ◽  
Infinite System ◽  
Energy Gap ◽  
Functional Theory ◽  
Molecular Diode ◽  
Current Voltage ◽  
P Type

A molecular diode based on a conjugated co-oligomer composed of p-type and n-type segments is investigated using the first principles method. The co-oligomer is connected to Au electrodes to form an Au –oligomer– Au system. The infinite system is dealt with a finite structure confined in a device region and effects from semi-infinite electrodes. Density functional theory and nonequilibrium Green's function are used to describe the device region self-consistently. The current–voltage (I–V) characteristics of the constructed system are calculated and a rectification behavior is observed. The energy gap and the spatial orientation of molecular orbitals, and the transmission functions are calculated to analyze the I–V characteristics of the molecular diode.

STRUCTURAL AND ELECTRONIC EVOLUTION FROM SiC SHEET TO SILICENE

2013 ◽  
Vol 27 (32) ◽  
pp. 1350188 ◽  
Author(s):  
G. LIU ◽  
M. S. WU ◽  
C. Y. OUYANG ◽  
B. XU
Keyword(s):  
Density Functional Theory ◽  
Fermi Level ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Band Gaps ◽  
Functional Theory ◽  
Orbital Contribution ◽  
Structural And Electronic Properties ◽  
Substitution Ratio

The evolution of the structural and electronic properties from SiC sheet to silicene is studied by using first-principles density functional theory. It is found that the planar configurations of the Si – C monolayer systems are basically kept except for the increase of the buckling of the planar structure when the substitution ratio of Si increases. Band gaps of the Si – C monolayer system decrease gradually when the substitution ratio of Si atoms ranges from 0% to 100%. The energy and type of the band gaps are closely related with the substitution ratio of Si atoms and the Si – C order. Further analysis of density of states reveals the orbital contribution of Si and C atoms near the Fermi level. The discussion of the electronic evolution from SiC sheet to silicene would widen the application of the Si – C monolayer systems in the optoelectronic field in the future nanotechnology.

A first principles study of the mechanical properties of Li–Sn alloys

RSC Advances ◽  
2015 ◽  
Vol 5 (45) ◽  
pp. 36022-36029 ◽  
Author(s):  
Panpan Zhang ◽  
Zengsheng Ma ◽  
Yan Wang ◽  
Youlan Zou ◽  
Weixin Lei ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Density Functional Theory ◽  
Failure Mechanism ◽  
First Principles ◽  
Density Functional ◽  
Elastic Moduli ◽  
Poisson's Ratio ◽  
Active Materials ◽  
Functional Theory ◽  
First Principles Study

Focusing on the failure mechanism of active materials during charging–discharging, the mechanical properties of Li–Sn alloys are studied by density functional theory, including elastic moduli, Poisson's ratio, anisotropy, and brittleness-ductility.

Stability and Electronic Structures of Mg2Pb (100), (110) and (111) Surfaces

2015 ◽  
Vol 817 ◽  
pp. 690-697
Author(s):  
Yong Hua Duan ◽  
Yong Sun ◽  
Ming Jun Peng
Keyword(s):  
Density Functional Theory ◽  
Surface Energy ◽  
Density Of States ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Dft Method ◽  
Functional Theory ◽  
Charge Density Difference ◽  
The Stability

The stability and electronic properties of Mg2Pb (100), (110) and (111) surfaces were investigated by using the first-principles density functional theory (DFT) method. The calculated results showed that the orders of relaxation and surface energy are |∆d15(111)| < |∆d15(110)| < |∆d15(100)| andEsurf(100) >Esurf(110) >Esurf(111), respectively, indicating that Mg2Pb (111) surface is the most stable among these three low index surfaces. The Density of states (DOS) of Mg2Pb surfaces are mainly dominated by Pb-6, Mg-3s, and 2porbitals in the band ranging from-5 eV to Fermi level. It can be further obtained from results of the DOS and the charge density difference that Mg2Pb (111) surface is more stable than Mg2Pb (100) and (110) surfaces. The Mg2Pb (111) surface is the thermodynamically most favorable over all of the range of.

scholarly journals First-principles insights on mechanical and electronic properties of TiX (X=C,N) in β-Si3N4 based ceramics

2016 ◽  
Vol 10 (3) ◽  
pp. 153-160 ◽  
Author(s):  
Harsha Shanmugakumar ◽  
Nagarajan Veerappan ◽  
Chandiramouli Ramanathan
Keyword(s):  
Density Functional Theory ◽  
Shear Modulus ◽  
Electronic Properties ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Si3n4 Ceramic ◽  
Functional Theory ◽  
Clear Insight ◽  
Si3n4 Ceramics

The mechanical and electronic properties of ?-Si3N4, TiC-Si3N4 and TiN-Si3N4 ceramics are investigated using density functional theory implemented with GGA/PBE functional. The pristine ?-Si3N4 exhibits fracture for a strain of 10%. However, TiC-Si3N4 and TiN-Si3N4 ceramics exhibits fracture for a strain of 20%. The Young?s modulus, shear modulus and bulk modulus of the pristine ?-Si3N4, TiC-Si3N4 and TiN-Si3N4 ceramics are reported. TiN-Si3N4 ceramic is found to be the least compressible and hard. The band gap is found to decrease for TiC-Si3N4 and TiN-Si3N4 ceramics comparedwith the pristine ?-Si3N4. The density of states spectrumshows more peak maxima for TiC-Si3N4 and TiN-Si3N4 ceramics rather than ?-Si3N4. The finding of the present work gives a clear insight on the mechanical and electronic properties of ?-Si3N4, TiC-Si3N4 and TiN-Si3N4 ceramics at the atomistic level.

scholarly journals First-Principles Study of the Structural Stability and Electronic and Elastic Properties of Helium inα-Zirconium

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Jian Zheng ◽  
Huijun Zhang ◽  
Xiaosong Zhou ◽  
Jianhua Liang ◽  
Liusi Sheng ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Elastic Properties ◽  
Density Of States ◽  
First Principles ◽  
Octahedral Site ◽  
Density Functional ◽  
Formation Energy ◽  
Interstitial Site ◽  
First Principles Calculations ◽  
Functional Theory

First-principles calculations within density functional theory have been performed to investigate the behaviors of helium inα-zirconium. The most favorable interstitial site for He inα-Zr is not an ordinary tetrahedral or octahedral site, but a basal octahedral site with a formation energy as low as 2.40 eV. The formation energy reduces to 1.25 eV in the presence of preexisting vacancies. The analysis on the density of states and the charge density has been carried out. In addition, the influences of He and small He-V complexes on the elastic properties have been studied. The He-V complexes have been found to greatly affect the elastic properties compared with He alone.

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