Quadratically convergent multiconfiguration Dirac-Fock and multireference relativistic configuration-interaction calculations for many-electron systems

A quadratically convergent Newton-Raphson algorithm for a relativistic,multiconfiguration Dirac-Fock self-consistent-field calculations is developed and implemented with analytic basis sets of Gaussian spinors. A procedure to perform second-order energy optimization for a general class of multiconfiguration wave functions constructed from one-particle Dirac spinors is described. We report the,results of relativistic multiconfiguration Dirac-Fock self-consistent-field calculations and relativistic multireference configuration-interaction calculations based on the multiconfiguration Dirac-Fock wave functions for the lowest P-3(0), P-3(1), and P-3(2) states of oxygenlike iron (Fe18+), ground J = 0 and excited J = 1 states of beryllium, and ground-state berylliumlike neon (Ne6+), species that exhibit the near degeneracy characteristic of a manifold of strongly interacting configurations. [S1063-651X(98)11309-0].