VBDFT(S) - A HUCKEL-TYPE SEMIEMPIRICAL VALENCE-BOND METHOD SCALED TO DENSITY-FUNCTIONAL ENERGIES - APPLICATION TO LINEAR POLYENES

A semi-empirical valence bond (VB) method, called VBDFT(s), is describ ed and applied to CnHn+2 conjugated hydrocarbons. The method is a Huck el-type VB scheme with energies scaled to density functional theory en ergies based on a single parameter; the matrix element lambda due to s pin transposition between bonded atoms. Total energies, excitation ene rgies, resonance and rr-bond energies are presented for the various sp ecies. The insight that can be derived from the corresponding wavefunc tions is discussed. (C) 1998 Elsevier Science B.V. All rights reserved .