Discussion on the variable Wolfsberg–Helmholtz parameter, a new simplified Löwdin transformation and the characteristic structure of the transformed EHT Hamiltonian matrices

AbstractThree related problems are discussed: (1) the variable nature of the Wolfsberg–Helmholtz parameter and its relationship with the overlap eigenvalue range; (2) the possibility of deriving an efficient framework, describing a simplified Löwdin transformation to solve generalized secular equations; and (3) the structure of the transformed classical EHT Hamiltonian. This work shows how the simplified Löwdin transformation permits expression of the resulting transformed Hamiltonian elements by means of inward matrix products and total matrix sums. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004