Relativistic self-consistent-field methods for molecules. III. All-electron calculations on diatomics HI, HI+, AtH, and AtH+

All-electron relativistic and nonrelativistic self-consistent-field programs have been developed and calculations on diatomics HI, HI+, AtH, and AtH+ have been performed to get the spectroscopic constants. The results of HI, HI+, and AtH agree fairly well with those by the effective-core potential methods. The relativistic contractions of bond lengths of AtH and AtH+ are found to be about 2%. Contrary to the common belief, the harmonic frequencies found from the relativistic calculations are smaller than those of the nonrelativistic calculations.