CALCULATIONS OF N-14 AND H-2 NUCLEAR QUADRUPOLAR COUPLING-CONSTANTS FOR LIQUID-AMMONIA

Nitrogen (N-14) and deuterium (H-2) nuclear quadrupolar coupling const ants, chi(N-14) and chi(H-2), 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 se t and cluster size dependence of the calculated results has been exami ned. The calculated value of chi(N-14) for liquid ammonia at 197 K, -3 .45 MHz, is found to be close to the accepted solid-state value. At 23 2 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 chi( H-2) for liquid ammonia are by about 20% smaller than the correspondin g values calculated for the gas-phase monomer. On the basis of the cal culations presented here and those of previous workers it is clear tha t the accepted experimental value of chi(H-2) for solid ammonia-, is t oo small.