Theoretical study on the electronic structure, mechanical property, and thermal expansion of yttrium oxysulfide

2015 ◽  
Vol 04 (01) ◽  
pp. 1550004
Author(s):  
Ruipeng Gao ◽  
Yefei Li
Keyword(s):  
Mechanical Property ◽  
Thermal Expansion ◽  
Electronic Structure ◽  
Bulk Modulus ◽  
Density Functional ◽  
Theoretical Study ◽  
Spherical Shape ◽  
Weak Anisotropy ◽  
Covalent Bonds ◽  
Very High

The electronic structure, mechanical property and thermal expansion of yttrium oxysulfide are calculated from first-principles using the theory of density functional. The calculated cohesive energy indicates its thermodynamic stable nature. From bond structure, the calculated bandgap is obtained as 2.7 eV; and strong covalent bonds exist between Y and O atoms intra 2D [ Y – O ] layer in material, while relatively weak covalent bonds also exist inter 2D [ Y – O ] layer and S atoms. From simulation, it is found that the bulk modulus is about 119.4 GPa for the elastic constants, and the bulk modulus shows weak anisotropy because the surface contours of them are close to a spherical shape. The calculated B/G clearly implies its ductile nature, and the Y 2 O 2 S phase can also be compressed easily. The temperature dependence of thermal expansions is mainly caused by the restoration of thermal energy due to lattice excitations at low temperature. When the temperature is very high, the thermal expansion coefficient increases linearly with temperature increasing. Meanwhile, the heat capacities are also calculated and discussed by thermal expansion and elasticity.

Meso-alkynyl corroles and their cobalt(III), manganese(III) and gallium(III) complexes

2020 ◽  
Vol 24 (05n07) ◽  
pp. 737-749
Author(s):  
Michael Haas ◽  
Sabrina Gonglach ◽  
Wolfgang Schöfberger
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Theoretical Study ◽  
Lumo Energy ◽  
Functional Theory ◽  
Energy Gaps ◽  
Peak Broadening ◽  
Homo And Lumo ◽  
Homo Lumo

We report routes towards synthesis of novel [Formula: see text]-conjugated freebase cobalt, copper, gallium and manganese meso-alkynylcorroles. UV-vis spectra show that extensive peak broadening, red shifts, and changes in the oscillator strength of absorptions increase with the extension of [Formula: see text]-conjugation. Using density functional theory (DFT), we have carried out a first theoretical study of the electronic structure of these metallocorroles. Decreased energy gaps of about 0.3–0.4 eV between the HOMO and LUMO orbitals compared to the corresponding copper, gallium and manganese meso-5,10,15 triphenylcorrole are observed. In all cases, the HOMO energies are nearly unperturbed as the [Formula: see text]-conjugation is expanded. The contraction of the HOMO–LUMO energy gaps is attributed to the lowered LUMO energies.

Theoretical Study of the Electronic Structures of Li-Doped ZnO

2012 ◽  
Vol 535-537 ◽  
pp. 214-218
Author(s):  
Qi Xin Wan ◽  
Jia Yi Chen ◽  
Zhi Hua Xiong ◽  
Dong Mei Li ◽  
Bi Lin Shao ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Formation Energy ◽  
Lattice Distortion ◽  
Theoretical Study ◽  
Functional Theory ◽  
Li Doping ◽  
The Density Functional Theory ◽  
Doped Zno ◽  
Good Agreement

The first-principles with pseudopotentials method based on the density functional theory was applied to calculate the geometric structure, the formation energy of impurities and the electronic structure of Li-doped ZnO. In the system of Li-doped ZnO, LiZn can not result in lattice distortion. In contrast with that case, LiO and Lii result in lattice distortion after Li doping in ZnO. In Li-doped ZnO, LiO is the most unstable than the other cases. Simultaneously, Lii is more stable than LiZn according to that Lii has smaller formation energy. Furthermore, the electronic structure of Li-doped ZnO indicates that that LiZn behaves as acceptor, while Lii behaves as donor. In conclusion, in Li-doped ZnO, Lii is always in the system to compensate the acceptor. Singly doping Li in ZnO is difficult to gain p-ZnO for the self-compensation. The results are in good agreement with other calculated and experimental results.

scholarly journals Theoretical study on crystal polymorphism and electronic structure of lead(ii) phthalocyanine using model dimers

RSC Advances ◽  
2017 ◽  
Vol 7 (14) ◽  
pp. 8646-8653 ◽  
Author(s):  
Nobutsugu Hamamoto ◽  
Hiromitsu Sonoda ◽  
Michinori Sumimoto ◽  
Kenji Hori ◽  
Hitoshi Fujimoto
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Theoretical Study ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Crystal Polymorphism ◽  
Small Models

The polymorphism in lead(ii) phthalocyanine solids was discussed with the results of density functional theory calculations using small models.

scholarly journals Unveiling the Atomic and Electronic Structure of Stacked-Cup Carbon Nanofibers

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
D. W. Boukhvalov ◽  
I. S. Zhidkov ◽  
A. Kiryakov ◽  
J. L. Menéndez ◽  
L. Fernández-García ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Carbon Nanofibers ◽  
Density Functional ◽  
Graphene Quantum Dots ◽  
Quantitative Agreement ◽  
Optical Measurements ◽  
Radiative Relaxation ◽  
Covalent Bonds ◽  
Band Spectra ◽  
Valence Bands

AbstractWe report results of comprehensive experimental exploration (X-ray photoemission, Raman and optical spectroscopy) of carbon nanofibers (CNFs) in combination with first-principles modeling. Core-level spectra demonstrate prevalence of sp2 hybridization of carbon atoms in CNF with a trace amount of carbon–oxygen bonds. The density functional theory (DFT)-based calculations demonstrated no visible difference between mono- and bilayers because σ-orbitals are related to in-plane covalent bonds. The influence of the distortions on π-peak is found to be significant only for bilayers as a result of π–π interlayer bonds formation. These results are supported by both experimental Raman and XPS valence band spectra. The combination of optical measurements with a theoretical modeling indicates the formation of optically active graphene quantum dots (GQDs) in the CNF matrix, with a radiative relaxation of the excited π* state. The calculated electronic structure of these GQDs is in quantitative agreement with the measured optical transitions and provides an explanation of the absence of visible contribution from these GQDs to the measured valence bands spectra.

First-Principles Study on Electronic Structure, Elasticity, Debye Temperature and Anisotropy of Cubic KCaF3

2020 ◽  
Vol 999 ◽  
pp. 109-116
Author(s):  
Xing Liu ◽  
Jia Fu ◽  
Man Man Han ◽  
Kai Xin Sun ◽  
Sheng Li Wei
Keyword(s):  
Electronic Structure ◽  
Debye Temperature ◽  
First Principles ◽  
Density Functional ◽  
Elastic Moduli ◽  
Poisson Ratio ◽  
Structural Parameters ◽  
Functional Material ◽  
Covalent Bonds ◽  
Functional Theory

As a potential functional material in the perovskite family, the KCaF3 on electronic structure, elasticity, Debye temperature and anisotropy are studied based on density functional theory (DFT). Above all, the structural parameters of KCaF3 crystal are optimized. Then the elastic constants and Debye temperature are calculated. The results show that: (1) KCaF3 is composed of covalent bonds, in which the Ca-F bond is stronger than K-F. (2) Ca atom mainly contributes for the electronic properties of KCaF3. (3) The structural parameters of KCaF3 is in fair agreement with the experimental data. (4) The anisotropy of KCaF3 was analyzed from the pure and quasi waves, of which the longitudinal wave velocity in the direction of [100] is the larger than the others two directions ([110] and [111]). Finally, The homogenized elastic moduli (bulk modulus B, shear modulus G, Young's modulus E), Pugh and Poisson ratio, are obtained. This research is meaningful and thus to provides a good theoretical guidance for the design the new ABX3-type material with better performance.

First Principles Investigation of Electronic Structure, Chemical Bonding, Elastic and Optical Properties of Novel Rhenium Nitrides

2012 ◽  
Vol 512-515 ◽  
pp. 883-889
Author(s):  
Qing Lin Xia ◽  
Liu Xian Pan ◽  
Yuan Dong Peng ◽  
Li Ya Li ◽  
Hong Zhong Wang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
Density Of States ◽  
Chemical Bonding ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Hexagonal Phase ◽  
Partial Density

we investigate the electronic structure, chemical bonding, optical and elastic properties of the novel rhenium nitrides, hexagonal phase re3n and re2n by using density-functional theory (dft) within generalized gradient approximation (gga). the calculated equilibrium lattice constants of both re3n and re2n are in reasonable agreement with the experimental results. the band structure along the higher symmetry axes in the Brillouin zone, the density of states (dos) and the partial density of states (pdos) are presented. the calculated energy band structures and dos show that re3n and re2n are metal compounds. The dos and pdos show that the dos at the fermi level (ef) is located at the bottom of a valley and originate mainly from the 5d electrons of re. population analyses suggest that the chemical bonding in re3n and re2n has predominantly covalent character with mixed covalent and ionic characteristics. the dielectric function, reflectivity, absorption coefficient, refractive index, electron energy-loss function and optical conductivity are presented in an energy range for discussing the optical properties of re3n and re2n. basic mechanical properties, such as elastic constants cij, bulk modulus b and shear modulus g are calculated. The young’s modulus e, poisson's ratio ν and bh/gh are also predicted. results conclude that the hexagonal phase re3n and re2n are mechanical stable and behaves in a ductile manner. polycrystalline elastic anisotropy is also derived from polycrystalline bulk modulus b and shear modulus g.

First-principles investigation of MoS2 monolayer adsorbed on SiO2 (0001) Surface

2017 ◽  
Vol 31 (25) ◽  
pp. 1750229 ◽  
Author(s):  
Xiangying Su ◽  
Hongling Cui ◽  
Weiwei Ju ◽  
Yongliang Yong ◽  
Xiaohong Li
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Charge Transfer ◽  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Interlayer Spacing ◽  
Covalent Bonds ◽  
Functional Theory ◽  
Mos2 Monolayer

In this paper, the geometric and electronic structure of MoS2 monolayer (ML) adsorbed on SiO2 (0001) surface were studied by using density functional theory calculations. The calculated interfacial binding energy shows that the MoS2/SiO2 hybrid system is stable. MoS2 ML is bound to the SiO2 surface with a big interlayer spacing and no covalent bonds form at the interface. The study of the density of states and the charge transfer indicates that the interaction between MoS2 ML and the SiO2 substrate is very weak. As a result, the electronic properties of MoS2 ML are almost not affected by the SiO2 substrate. This work will be beneficial to the design of MoS2 ML-based devices where a substrate is needed.

Electronic and Structural Properties of Si46: A Novel Solid of Silicon Fullerenes

1994 ◽  
Vol 358 ◽  
Author(s):  
Susumu Saito ◽  
Atsushi Oshiyama
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Level Density ◽  
Functional Theory ◽  
Metal Atoms ◽  
The Density Functional Theory ◽  
Real Geometry ◽  
Electronic And Structural Properties ◽  
New Si ◽  
Very High

ABSTRACTWe report the electronic structure of the S46 lattice having a just lnm-size unit cell and has been optimized within the density-functional theory. The Si46 lattice studied is the real geometry of Si atoms crystallized with metal atoms, and consists essentially of dodecahedral-cage Si20 fullerenes proposed by us previously. Although all the Si atoms are tetrahedrally coordinated, its electronic structure is found to be considerably different from that of the diamond Si lattice due to the pentagonal Si-Si network. Si46 is an important new Si semiconductor to be synthesized in the future. We also report the electronic structure of Na2Ba6Si46. The material is found to be metallic and the Fermi-level density of states is very high due to the hybridization between Si and Ba states, which should be of essential importance for the superconductivity observed in Na and Ba codoped Si46.

Stability, Electronic and Magnetic Properties of Ca3Ru2O7

2011 ◽  
Vol 217-218 ◽  
pp. 924-929
Author(s):  
Jin Hong Xue ◽  
Jing Chao Chen ◽  
Jie Yu ◽  
Jing Feng ◽  
Yong Pan ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Magnetic Properties ◽  
Cohesive Energy ◽  
Density Functional ◽  
Theoretical Study ◽  
Magnetic Moments ◽  
Covalent Bonds ◽  
Functional Theory ◽  
Electronic And Magnetic Properties ◽  
The Stability

Ca3Ru2O7 is new tpye of thermoelectric materials.A theoretical study is presented for the stability, electronic and magnetic properties of three phases of this new thermoelectric materials in the framework of density functional theory (DFT). The calculated cohesive energy is -7.94eV/unit. AFM2 are less stable than other pahses. Electronic calculations indicate that Ca3Ru2O7 is metallic in nature. The covalent bonds in these structures are due to orbital overlap between p bands of O and d bands of Ru, and DOS at Fermi level are dominated by d bands of Ru. FM phase have obvious magnetic moments.

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