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.