CHARGE DENSITY STUDIES OF TRANSITION METAL SULFIDES. Zhengwei Su and Philip Coppens (Chemistry Department, State University of New York at Buffalo, Buffalo, NY 14260) Nobuo Ishizawa (Tokyo Institute of Technology, Yokohama 226, Japan) and Natalie Holzwarth and Yueping Zeng (Physics Department, Wake Forest University, Winston-Salem, NC 27109).
The electron density distributions of transition metal sulfides MS2 (pyrite structure) for M = Mn, Fe, Co, and Ni have been analyzed by multipole refinement and topological analysis using the XD program package (1), with data reported previously (2). The metal d-orbital populations and deformation density maps confirm that the transition metal in MnS2 is in a high spin state, while low spin states occur in the other solids. The electron density at the M-S bond critical points decreases as the bond length increases, indicating decreasing bond strength. The Laplacians at the S-S and M-S bond critical points are all positive. Their values do not correlate well with the bond lengths or densities. The structure factors from a theoretical DFT calculation on FeS2 (3), have been analyzed with the multipole formalism. Experimental and theoretical multipole parameters and density maps will be compared.
The effect of the use of selection of different form factors (non-relativistic, relativistic and modified relativistic) will be discussed.
References
1. XD, a computer program package for multipole refinement and analysis of electron densities from diffraction data, T. Koritsanszky, S. Howard, P. R. Mallinson, Z. Su, T. Richter and N. K. Hansen, 1995.
2. E. D. Stevens, M. L. DeLucia and P. Coppens, Inorg. Chem. 19, 813-820 (1980). (FeS2) data; E. Nowack, D. Schwarzenbach and T. Hahn, Acta Cryst. B47, 650-659 (1991). (CoS2 and NiS2 data); U. Ueki, N. Ishizawa and F. Marumo. Presented at the AsCA Meeting, Bangkok, Thailand (1995). (MnS2 data).
3. Y. Zeng and N. A. W. Holzwarth, Phys. Rev. B50, 8214 (1994).
Support of this work by the National Science Foundation (CHE9317770) is gratefully acknowledged.