Polymorphism and second harmonic generation in a novel diamond-like semiconductor: Li2MnSnS4

초록

High-temperature, solid-state synthesis in the Li2MnSnS4 system led to the discovery of two new polymorphic compounds that were analyzed using single crystal X-ray diffraction. The alpha-polymorph crystallizes in Pna2(1) with the lithium cobalt (II) silicate, Li2CoSiO4, structure type, where Z=4, R1=0.0349 and wR2 =0.0514 for all data. The beta-polymorph possesses the wurtz-kesterite structure type, crystallizing in Psi with Z=2, R1=0.0423, and wR2= 0.0901 for all data. Rietveld refinement of synchrotron X-ray powder diffraction was utilized to quantify the phase fractions of the polymorphs in the reaction products. The alpha/beta-Li2MnSnS4 mixture exhibits an absorption edge of similar to 2.6-3.0 eV, a wide region of optical transparency in the mid- to far-IR, and moderate SHG activity over the fundamental range of 1.1-2.1 mu m. Calculations using density functional theory indicate that the ground state energies and electronic structures for alpha- and beta-Li2MnSnS4, as well as the hypothetical polymorph, gamma-Li2MnSnS4 with the wurtz-stannite structure type, are highly similar. 2015 Elsevier Inc. All rights reserved.

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