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Infrared absorption spectra of the perovskite fluorides KMF3(M:Ni, Mg, and Zn) and NaNiF3 have been measured in the region 700 to 50 cm−1 at room temperature and liquid‐nitrogen temperature. Three absorption bands for KMF3 were observed and these have been assigned to the f1u lattice modes. A normal‐coordinate analysis of the crystal as a whole has been performed and the interatomic force constants in the crystal have been obtained. The forms of the normal modes of the lattice vibrations have been fully described on the basis of the normal‐coordinate treatment. Vibrational assignments have been supported from the experimental ground (temperature effect) and the theoretical side. The compound NaNiF3 reveals a much more complicated spectrum than those of KMF3, which suggests a structure of an appreciable deformation from the regular cubic perovskite. The analysis of the lattice vibrations for the rutile counterparts has been made based on the normal‐coordinate treatment by the use of the force constants tra...

Nonempirical calculations of the electronic structure of the ammonia molecule are carried out using a ``bond‐orbital'' and a ``modified electron‐pair'' function. The calculated binding energies are 0.348 a.u. (76% of the experimental value) and 0.381 a.u. (83%), respectively. The best theoretical value previously known was 0.378 a.u., the result of a self‐consistent LCAO calculation including limited configuration interaction.It is concluded that the ``modified electron‐pair'' function is an adequate simple approximation, and the ``frozen core'' approximation employed in the calculation is satisfactory.The dipole moment is also calculated, and reasonable agreement with the experimental value is obtained.