Ab initio calculations of the anionic sodium-ammonia complex

The structure, stability and vibrational frequencies of (NaNH3)− and (NaND3)− are examined by ab initio MP2 and CISD methods. It was found that the two C3v isomers I and II have an Na−⋯NH3 dissociation energy De = 1135 cm−1 (I) and De = 1028 cm−1 (II). However, their vibrational frequencies are quite different. After consideration of the zero-point energy, the dissociation energy D0 of isomer II is slightly larger than for isomer I.