Gradients in valence bond theory

A gradient method for general valence bond wave functions is presented. The electronic energy is used as a Lagrange multiplier. The derivatives of the normalization and of the first- and second-order cofactors present in the energy expression have to be evaluated, giving rise to first-, second-, and third-order cofactors. This evaluation is done using an extension of metho ds described previously. The use of gradients is illustrated with some calc ulations on organic molecules, viz. ethene, 1, 4-butadiene, and benzene. (C ) 2000 American Institute of Physics. [S0021-9606(00)31230-2].