A GENERALIZED DIRECT INVERSION IN THE ITERATIVE SUBSPACE APPROACH FORGENERALIZED VALENCE-BOND WAVE-FUNCTIONS

We present a greatly improved method for converging generalized valenc e bond (GVB) self-consistent wave functions. This method starts with t he direct inversion in the interative subspace (DIIS) ideas of Pulay. Previously implemented DIIS methods were limited to special cases: clo sed-shell Hartree-Fock (HF), restricted open-shell HF, or a single pai r GVB wave function. Here we extend this method to general wave functi ons including arbitrary numbers of closed-shell, restricted open-shell , and GVB orbitals (including second-order orbital mixing terms). The efficacy of GVB-DIIS is illustrated by applying it to several cases (i ncluding GVB wave functions with up to ten pairs) and comparing with o ther standard methods.