Synthesis, crystal and electronic structures, nonlinear optical properties, and magnetic properties of two thiophosphates: KInP(_2)S(_7) and KCrP(_2)S(_7)

Thumbnail Image
Issue Date
Cropek, Craig
Nguyen, Vivian
Chhetri, Santosh K.
Hu, Jin
Guo, Sheng-Ping
Wang, Jian

Cropek, C.; Nguyen, V.; Chhetri, S.K.; Hu, J.; Guo, S.; Wang, J. Synthesis, Crystal and Electronic Structures, Nonlinear Optical Properties, and Magnetic Properties of Two Thiophosphates: KInP2S7 and KCrP2S7. Crystals 2022, 12, 1505.


Two thiophosphates, KInP(_2)S(_7) and KCrP(_2)S(_7), were structurally characterized without investigating any optical properties. Herein in this work, KInP(_2)S(_7) and KCrP(_2)S(_7) were revisited to investigate their optical and magnetic properties, respectively. Pure polycrystalline samples and crystals of KInP(_2)S(_7) and KCr(_2)S(_7) were grown by high temperature solid state reactions, where mm-sized crystals of KCrP(_2)S(_7) were collected. KCrP(_2)S(_7) is isostructural to KInP(_2)S(_7), which features a layered structure. KInP(_2)S(_7) and KCrP(_2)S(_7) possess close relationship to the layered thiophosphate M(_2)P(_2)S(_6) (M = Fe, Co, Zn, etc.). The bonding pictures of KInP(_2)S(_7) were studied using the electron localization function (ELF) coupled with crystal orbital Hamilton population (COHP) calculations. The intrinsically distorted [PS(_4)] tetrahedra and [InS(_6)] octahedra are made by strong covalent P-S interactions and ionic In-S interactions, respectively. Electronic structure analysis confirmed that the optical properties of KInP(_2)S(_7) are mainly contributed to by [PS(_4)] tetrahedra together with small amounts of the contributions coming from [InS(_6)] octahedra. Magnetic measurement on mm-sized crystals of KCrP(_2)S(_7) verified that there is an antiferromagnetic transition around 21 K, and the Cr atoms are trivalent. KInP(_2)S(_7) is predicated to be an indirect bandgap semiconductor of 2.38 eV, which is confirmed by the UV-Vis measurement of 2.4(1) eV. KInP(_2)S(_7) is not a type-I phase-matching material and exhibits moderate second harmonic generation (SHG) response (0.51 × AgGaS(_2), sample of particle size of 100 µm). The laser damage threshold (LDT) of KInP(_2)S(_7) is very high of 5.2 × AgGaS(_2). Bandgap engineering were undergone to enhance the SHG response of KInP(_2)S(_7).

Table of Content
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (