Papers by Keyword: Density Function Theory (DFT)

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Authors: Yoshitaka Umeno, Kuniaki Yagi, Hiroyuki Nagasawa
Abstract: We carry out ab initio density functional theory calculations to investigate the fundamental mechanical properties of stacking faults in 3C-SiC, including the effect of stress and doping atoms (substitution of C by N or Si). Stress induced by stacking fault (SF) formation is quantitatively evaluated. Extrinsic SFs containing double and triple SiC layers are found to be slightly more stable than the single-layer extrinsic SF, supporting experimental observation. Effect of tensile or compressive stress on SF energies is found to be marginal. Neglecting the effect of local strain induced by doping, N doping around an SF obviously increase the SF formation energy, while SFs seem to be easily formed in Si-rich SiC.
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Authors: M.V. Magnitskaya, E.T. Kulatov, A.A. Titov, Y.A. Uspenskii, E.G. Maksimov, S.V. Popova, V.V. Brazhkin
Abstract: We report on ab initio density-functional calculations of a novel spintronics-related compound CrGa2Sb2 recently synthesized under high pressure. The effect of Cr deficiency on the electronic, magnetic and optical properties of CrGa2Sb2 is considered. New X-ray structural measurements up to high pressure of 9 GPa are presented.
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Authors: C. Kanagaraj, Baskaran Natesan
Abstract: We have performed detailed structural, electronic and magnetic properties of high - TC multiferroic CuO using first principles density functional theory. The total energy results revealed that AFM is the most stable magnetic ground state of CuO. The DOS and electronic band structure calculations show that in the absence of on-site Coulomb interaction (U), AFM structure of CuO heads to a metallic state. However, upon incorporating U in the calculations, a band gap of 1.2 eV is recovered. Furthermore, the Born effective charges calculated on Cu does not show any anomalous character.This suggests that the polarization seen in CuO could be attributed to the spin induced AFM ordering effect.
129
Authors: Gui Fa Li, Shi Qiang Lu, Jun Wei Liu, Ping Peng
Abstract: Based on the method of LST/QST improved in the molecular orbital DMol3 program, with the aid of the minimum energy path (MEP) in the climbing image nudged elastic band (CI-NEB) method, the Oh-Al13 cluster is investigated under different synthesis process, i.e. Al6+Al7→Al13. The results show that: there are two stages in the synthesis reaction: the distortion stage and the configuration revolution stage. In the first stage, the metastable structures are forced to change into stable structures. In the configuration evolution stage, two different cases exist. For the synthesis of crystal clusters it is an automatic exothermic reaction if all reactants being of typical crystal symmetrical elements, i.e., Al6+Al7M®Oh-Al13. While an energy barrier must be overcome if one of reactants having fivefold or tenfold symmetrical axes, i.e.,Al6+Al7、Al6M+Al7 and Al6M+Al7M . So the five-symmetry structures are only appearing in rapidly solidified processes except crystallization processes.
586
Authors: Cheng Gen Zhang, Shu Yuan Yu, Zong Ji Cao
Abstract: Density functional theory (DFT) calculations were performed to investigate the structures of chloro silsesquioxanes Si2nO3nCl2n (n=1-5). Our study focuses on the structures, stabilities, and electronic properties of the chloro silsesquioxanes. The large HOMO–LUMO gaps, which range from 4.54 to 7.39 eV, imply optimal electronic structures for these molecules.
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Authors: Shu Yuan Yu, Cheng Gen Zhang, Ya Lan Wang
Abstract: Density functional theory (DFT) calculations were performed to investigate the structures of trifluoromethyl silsesquioxanes Si2nO3n(CF3)2n (n=1-5). Our study focuses on the structures, stabilities, and electronic properties of the trifluoromethyl silsesquioxanes. The large HOMO–LUMO gaps, which range from 5.38 to 8.02 eV, imply optimal electronic structures for these molecules.
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Authors: Zong Lin Liu, Hong Kuan Yuan, Hong Chen
Abstract: The geometric, electronic, and magnetic properties of Ho-doped Sin (n=1-12, 16, and 18) clusters are studied via the density functional theory with the generalized gradient approximation. The results show that the Ho atom in the most stable HoSin clusters always occupies the surface site. Starting from n=18, the Ho atom abruptly drops into the center of Si frame, forming the Ho-encapsulated Si cages. The stabilities of HoSin clusters increase with increasing size n. The Ho atom in HoSin clusters enhances their chemical activities. Moreover, the magnetisms of HoSin clusters are independent of their geometric structures, and the Si and Ho atoms are antiferromagnetic.
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Authors: Yan Wei, Jia Xin Xu, Xiao Mei Yuan, Xiao Hui Zheng
Abstract: We have studied the structures and electronic properties of PdCn (n=2-12) using the density functional theory in this paper. Though calculating, we found that the linear isomers are most stable for PdCn(n=2-9) clusters. N=10 is turning point, and the bicyclical structure is most stable for PdC10 cluster. Cyclic structures have the lowest energy for PdC11 and PdC12 clusters.
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Authors: Shuai Qin Yu, Yan Hua Fan, Li Hua Dong, Yan Sheng Yin
Abstract: Theoretical study on the geometric structures and magnetic properties of small (FeAl)n (n=1-4) clusters has been carried out at the BPW91 level. In all the (FeAl)n clusters, the iron atoms are brought together, yielding a maximum of Fe-Fe bonds, and the aluminum atoms are located around a Fe core with a maximum of Fe-Al bonds which is different the bulk ordered FeAl alloy dominated by the Fe-Al bonds. As opposed to the bulk FeAl with non-magnetic, the small nano-clusters are highly magnetic moment dominated by Fe-Fe clustering.
851
Authors: Himadri R. Soni, Prafulla K. Jha
Abstract: Using first principles density functional theoretical calculations within the generalized gradient approximation (GGA), the present paper reports thermal properties such as constant volume lattice specific heat, Gibbs free energy, internal energy, and entropy of Yb-pnictides such as YbN, YbP and YbAs in its rocksalt phase. The variation of lattice specific heat with temperature obeys the classical Dulong-Petits law at high temperature while at low temperature it obeys Debye T3 law. The internal energy, entropy and free energy show a gradual variation with temperature. The specific heat at constant volume at lower temperature increases as going from N to P to As. *Corresponding author Email: pkj@bhavuni.edu, prafullaj@yahoo.com Telephone: +91-278-2422650 Fax: +91-278-2426706
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