Инд. авторы:	Yelisseyev P., Solntsev V.P., Jiang X.X., Bekker T.B., Lin Z.S., Fedorov P.P.
Заглавие:	Electronic structure, magnetic and optical properties of the Ba-7(BO3)(4-x)F2+3x crystal
Библ. ссылка:	Yelisseyev P., Solntsev V.P., Jiang X.X., Bekker T.B., Lin Z.S., Fedorov P.P. Electronic structure, magnetic and optical properties of the Ba-7(BO3)(4-x)F2+3x crystal // Journal of Solid State Chemistry. - 2015. - Vol.229. - P.358-365. - ISSN 0022-4596. - EISSN 1095-726X.
Внешние системы:	DOI: 10.1016/j.jssc.2015.06.014; РИНЦ: 23973626; SCOPUS: 2-s2.0-84933557248; WoS: 000358815100046;
Реферат:	eng: Large size Ba-7(BO3)(4-x)F2+3x (x=0.49) single crystals of optical quality, up to 20 mm in size, were grown. Crystals exhibit a wide transparent spectral range from 0.215 to 6.6 mu m with the indirect energy band gaps of 4.97 and 5.09 eV at 300 and 80 K, respectively. X-ray irradiation can induce strong absorption in crystals in the UV to near IR regions, mainly from four types of paramagnetic centers: two hole-type centers where oxygen near some defect is ionized (O-(X) over bar1 or O-(1) over bar) and two electron-type centers where fluorine vacancies capture electrons (e((6) over bar) and e((4) over bar)). The electron spin resonance analysis and first-principles studies identified the detailed optical transitions in these centers. The induced absorption can be removed by illumination with photon energy 2.5 < hv < 4.5 eV or after heating to 450 K. The electronic structure calculations reveal that in Ba-7(BO3)(4-x)F2+3x both the top of valence bands and the bottom of conduction bands are composed of B 2p and O 2p orbitals. The linear and nonlinear optical properties are dominantly determined by the electron transition within (BO3)(3-) groups. Nonlinear susceptibility and birefringence are predicted to be d(31) =0.14 pm/V and 0.016 at x=0.25 and decrease to 0.01 and 0.011, respectively, as x grows to 0.75, due to the increase of F content in Ba-7(BO3)(4-x)F2+3x. (C) 2015 Elsevier Inc. All rights reserved.
Ключевые слова:	EXCHANGE; MECHANISM; BETA-BAB2O4; BORATE CRYSTALS; GENERALIZED GRADIENT APPROXIMATION; Linear and nonlinear optical properties; Electronic structure; Electron spin resonance; Vacancy; Optical absorption; Ba fluoroborate; SYSTEM;
Издано:	2015
Физ. характеристика:	с.358-365