Hartree–Fock and DFT calculations of quadrupole coupling constants in water clusters and ice Original Research Article

Periodic ab initio calculations of the 17O and 2H quadrupole coupling constants (QCC) and their shifts have been performed for ice VIII and ice IX. Cluster calculations were done for smaller water clusters and chains. The ice VIII crystal structure was optimized at the Hartree–Fock and BLYP (DFT) levels with a 6-311g** basis. Out of the methods tested here the Hartree–Fock-computed QCC shifts based on the fully optimized Hartree–Fock structure are those which overall agree best (within 5–10%) with experimental shifts. The crystalline surroundings outside the tetrahedral ice cluster accounts for between a third and a half of the observed experimental QCC downshifts for both oxygen and hydrogen in ice VIII.