A theoretical investigation of the equilibrium electric dipole moment of ammonia

From a series of highly accurate ab initio calculations, the non-relativistic CCSD(T) basis set limit value of the equilibrium electric dipole moment (μe) of NH3 has been determined. Further, the small effects of relativity and correlation beyond the CCSD(T) level on μe have been estimated. The ab initio results strongly suggest that the recent experimental value of 1.561 D for μe is too high and that the true value is closer to 1.533 D. A possible resolution of this discrepancy in terms of the experimental observations is proposed.