Flexibility of the MPS−4 Chains of the KMPS4 (M=Ni, Pd) Compounds Studied by Molecular Orbital Calculations and Atomic Force Microscopy Measurements

Abstract The flexibility of the M PS − 4 chains of K M PS 4 ( M =Ni, Pd) was examined by performing contact mode atomic force microscopy (AFM) measurements for the (001) surface of KNiPS 4 and also by performing extended Huckel tight binding calculations for the [ M (PS 4 ) 2 ] 4− entities of KMPS 4 . The observed AFM images were analyzed by calculating the total electron density plots for an isolated [NiPS 4 ] − slab of the (001) surface. Our calculations show that the PS 3− 4 ions are more strongly bound to the Pd 2+ ions in KPdPS 4 than to the Ni 2+ ions in KNiPS 4 , and that the bonding between the PS 3− 4 anions and M 2+ ( M =Ni, Pd) cations is flexible with respect to the rotational motions of the PS 3− 4 anions. The AFM images recorded for the (001) surface of KNiPS 4 indicate that the PS 3− 4 anions on the surface undergo a rotational relaxation when the scanning tip passes by.