Calculations of ~(14)N and ~2H Nuclear Quadrupolar Coupling Constants for Liquid Ammonia

摘要

Nitrogen (~(14)N) and deuterium (~2H) nuclear quadrupolar coupling constants, χ(~(14)N) and χ(~2H), have been calculated for liquid ammonia at 197 K, 232 K, and 271 K, using a combination of molecular dynamics simulations and ab initio molecular orbital calculations. The basis set and cluster size dependence of the calculated results has been examined. The calculated value of χ(~(14)N) for liquid ammonia at 197 K, —3.45 MHz, is found to be close to the accepted solid-state value. At 232 K and 271 K, the magnitudes of the calculated values are about 5-10% greater: -3.56 MHz and —3.67 MHz, respectively, but still well below the accepted gas-phase value, —4.09 MHz. The calculated values of χ(~2H) for liquid ammonia are by about 20% smaller than the corresponding values calculated for the gas-phase monomer. On the basis of the calculations presented here and those of previous workers it is clear that.the accepted experimental value of χ(~2H) for solid ammonia-d_3 is too small.