LiGaGe₂Se₆: A New IR Nonlinear Optical Material with Low Melting Point

Abstract

The new compound LiGaGe(2)Se(6) has been synthesized. It crystallizes in the orthorhombic space group Fdd2 with a = 12.501(3) Å, b = 23.683(5) Å, c = 7.1196(14) Å, and Z = 8. The structure is a three-dimensional framework composed of corner-sharing LiSe(4), GaSe(4), and GeSe(4) tetrahedra. The compound exhibits a powder second harmonic generation signal at 2 μm that is about half that of the benchmark material AgGaSe(2) and possesses a wide band gap of about 2.64(2) eV. LiGaGe(2)Se(6) melts congruently at a rather low temperature of 710 °C, which indicates that bulk crystals can be obtained by the Bridgman-Stockbarger technique. According to a first-principles calculation, there is strong hybridization of the 4s and 4p orbitals of Ga, Ge, and Se around the Fermi level. The calculated birefractive index is Δn = 0.04 for λ ≥ 1 μm, and the calculated major SHG tensor elements are d(15) = 18.6 pm/V and d(33) = 12.8 pm/V. This new material is promising for application in IR nonlinear optics.

Optical and electronic properties of lithium thiogallate (LiGaS2): experiment and theory

“…Due to the discontinuity of the exchange-correlation potential or the over-delocalization of the valence band (VB) in the GGA/LDA calculation, the LiGaS 2 band gap is about 1 eV smaller than the experimental data. 10,[21][22][23][24]55,56 The experimental band gap of LiGaS 2 can be 3.93 eV, 4.03 eV, and 4.15 eV, depending on temperature and the thickness of sample. 10,57,58 To achieve consistency between theory and experiment, the atomic positions in LiGaS 2 were taken from an experimental study which and correction is added to the exchange effect in the TB-mBJ method.…”

Vibration uncoupling of germanium with different valence states lowers thermal conductivity of Cs2Ge3Ga6Se14

“…For instance, the Ge 4+ tends to adopt a tetrahedral coordination with four nearly equidistant Ge-Q (Q = S, Se, Te) bonds [12][13][14][15][16][17][18][19], the Ge 3+ usually forms a Ge-Ge metal bond to fulfill its four coordination and generate the characteristic ethane-like Ge 3+ 2 Q 6 dimer [20][21][22][23][24][25][26][27], and the Ge 2+ is often found in an octahedron with six Ge-Q bonds [27,30]. Various arrangements of these structure building units lead to great diversity of structures [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Herein, we report a new compound of the Cs 2 Ge 3 M 6 Q 14 (M = Ga, In; Q = Se, Te) family, Cs 2 Ge 3 Ga 6 Se 14 , in which Ge 3+ and Ge 2+ coexist.…”

Sn2SiS4, synthesis, structure, optical and electronic properties

“…Recently, metal chalcogenides containing the group 14 elements, in particular the Sn metal, have received increasing interest [1][2][3][4][5][6][7][8][9][10][11]. Sn atom can be stabilized at both the +2 oxidation state with an electron lone pair and the +4 oxidation states without the lone pair electrons in chalcogenides.…”