Parr and Chattaraj proposed a principle of maximum hardness for stable
molecular structures. Pearson and Palke used ab initio SCF MO calcula
tions for ammonia and ethane to demonstrate the operation of the princ
iple. In this paper, we present ab initio SCF MO results for five isom
eric forms of the homoatomic P-6 cluster as further support for the pr
inciple of maximum hardness. (C) 1994 John Wiley & Sons, Inc.