The Hylleraas-CI method in molecular calculations. III. Implementation and numerical verification of a three-electron many-center theory

The general theory of three-electron Hylleraas-Configuration-Interaction method using linear correlation factors of the form r_ij has been implemented for molecular systems using cartesian Gaussians as basis sets. A brief review of the theory and the form of the three-electron integrals is presented. Additionally, a table of numerical values of some selected three-electron integrals is given. Results from test calculations on H₃ using the full form of the theory are presented for some simple basis sets. A discussion of the computational problems that need to be overcome before this approach is competitive with traditional methods is included.