Electronic Structure of LiH According to a Generalization of the Valence-Bond Method

The wavefunction of LiH has been calculated according to a generalization of the valence-bond method, called the G1 method, which leads to significantly better energies than the Hartree–Fock method, yet retains an independent-particle interpretation. The total energy of the LiH G1 wavefunction is – 8.017 a.u., which accounts for 36% of the difference between the Hartree–Fock and experimental energies. The G1 molecular orbitals, which are discussed in detail, correspond closely to chemists' intuitive concepts of electron orbitals and display bonding properties more clearly than do the Hartree–Fock orbitals. In particular, the bonding orbitals are nodeless between the nuclei and, when compared to the corresponding atomic orbitals, show increased amplitude over essentially the entire internuclear region. Finally, several one-electron properties calculated from the G1 wavefunction are presented.