DIRAC-FOCK-SLATER CALCULATIONS FOR DIATOMIC-MOLECULES WITH A FINITE-ELEMENT DEFECT CORRECTION METHOD (FEM-DKM)

The finite element method (FEM) has been developed into an accurate to ol for non-relativistic and relativistic single-particle type descript ions of atoms and diatomic molecules, which has become quite fast. Nev ertheless, the efficiency remained unsatisfactory in that most of the FEM points were used up in the core regions even though the molecular orbitals there are atomic-like and simply structured. The joint functi onal set consisting of atomic orbitals used for an LCAO trial wavefunc tion and the finite element basis for good convergence, employed as a defect correction method (DKM), remedies this deficiency; the computat ional effort scales basically linearly with the number of FEM points. Using the DKM we reached the same accuracy about an order faster than with pure FEM. (C) 1998 Elsevier Science B.V. All rights reserved.