Theoretical studies of the vibrational spectra and relaxation dynamics of ice and water

Recently, theoretical studies of condensed phase water have been advanced in two-fold, with the development of first the Wang-Huang-Braams-Bowman(WHBB) ab initio potential energy(PES) and dipole moment surfaces(DMS), and second the quantum Local-Monomer Model. The WHBB PES accurately describes the electronic energy of arbitrary number of water monomers using a many-body representation. The important intrinsic 2-body and 3-body interactions are permutationally invariant fits of tens of thousands ab initio energies. Very recently, a new dipole moment surface is reported using a spectroscopically accurate 1-body DMS and an intrinsic 2-body DMS fit. The quantum Local-Monomer Model uses a divide-and-conquer strategy and solves the Schrodinger equation for each water monomer embedded in its hydrated environment. This approach effectively reduces the formidable dimensionality of the condensed phase water to usually 3 to 6 and up to 9 degrees of freedom. The first half of the dissertation will review and formulate the WHBB PES and DMS and the Local-Monomer Model.;In the second half of the dissertation, we take advantage of this recent theoretical advancement and report several fully ab initio quantum studies of the vibrational spectra and dynamics of ice, liquid water and water hexamer. The topics include the infrared spectra of ice Ih and amorphous ice, vibrational density of states of neat and deuterated ice Ih and vibrational energy relaxation dynamics of HOD diluted ice, the infrared spectra of liquid water, and the infrared spectra and harmonic zero-point energies of HOD doped water hexamers.