Author： Shi-Chang Li Yuan-Lei Zheng Sheng-Gui Ma Tao Gao Bing-Yun Ao
Publisher： IOP Publishing
E-ISSN： 1741-4199|24|12|127101-127107
ISSN： 1674-1056
Source： Chinese Physics B, Vol.24, Iss.12, 2015-12, pp. : 127101-127107
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Abstract
The electronic structure, magnetic states, chemical bonding, and thermodynamic properties of β-US2 are investigated by using first-principles calculation through the density functional theory (DFT) +U approach. The obtained band structure exhibits a direct band gap semiconductor at Γ point with a band gap of 0.9 eV for β-US2, which is in good agreement with the recent experimental data. The charge-density differences, the Bader charge analysis, and the Born effective charges suggest that the U–S bonds of the β-US2 have a mixture of covalent and ionic characters, but the ionic character is stronger than covalent character. The Raman-active, infrared-active, and silent modes at the Γ point are further assigned and discussed. The obtained optical-mode frequencies indicate that the three apparent LO–TO (longitudinal optical–transverse optical) splittings occur in B1u, B2u, and B3u modes, respectively. Furthermore, the Helmholtz free energy ∆F, the specific heat ∆E, vibrational entropy S, and constant volume CV are studied over a range from 0 K∼100 K. We expect that our work can provide some valuable information for further experimental investigation of the dielectric properties and the infrared reflectivity spectrum of uranium chalcogenide.
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