Synthesis, crystal structures and physical properties of Ax(H2O)yMoS2(A = K, Rb, Cs)

Recently, metastable polymorphs of MoS2 (1T, 1T', 1T''') have raised much attention due to their rich crystal structures and intriguing physicochemical properties. They are often derived from alkali metal intercalated compounds of MoS2, A(x)(H2O)(y)MoS2 (A = alkali metal), by topotactic reaction. In order to make clear the deintercalation process, it is demanded to elucidate the compositions and crystal structures of A(x)(H2O)(y)MoS2. Here, we report the synthesis of high-quality A(x)(H2O)(y)MoS2 (A = K, Rb, Cs) single crystals, determine their crystal structures and investigate the physical properties. The three new quasi two-dimensional compounds crystallize in the identical monoclinic P2(1)/m (No.11) space group determined by single crystal X-ray diffraction. Their structures consist of ordered MoS2 layers, which are intercalated by disordered hydrated A' cations. Each layer contains edge-sharing [MoS6] octahedral, forming one-dimensional Mo zigzag chains along the b-axis. The resistivity of A(x)(H2O)(y)MoS2 increases with the decrease of temperature, which is the typical semiconducting behavior. The apparent difference in the resistivity of the three compounds is mainly related to the number of electrons injected by alkali metal atoms. Magnetic measurements indicated that the three compounds are dominantly paramagnetic accompanied by weak ferromagnetic contributions.