Flexibility of the MPS4- chains of the KMPS4 (M = Ni, Pd) compounds studied by molecular orbital calculations and atomic force microscopy measurements

The flexibility of the MPS; chains of KMPS4, (M = Ni, Pd) was examined by p erforming contact mode atomic force microscopy (AFM) measurements for the ( 001) surface of KNiPS4, and also by performing extended Huckel tight bindin g calculations for the [M(PS4)(2)](4-) entities of KMPS4. The observed AFM images were analyzed by calculating the total electron density plots for an isolated [NiPS4](-), slab of the (001) surface. Our calculations show that the PS43- ions are more strongly bound to the Pd2+ ions in KPdPS4, than to the Ni2+ ions in KNiPS4, and that the bonding between the PS43- anions and M2+ (M = Ni, Pd) cations is flexible with respect to the rotational motion s of the PS:- anions, The AFM images recorded for the (001) surface of KNIP S4, indicate that the PS43- anions on the surface undergo a rotational rela xation when the scanning tip passes by. (C) 1999 Academic Press.