THE COTTON-MOUTON EFFECT OF LIQUID WATER - PART-II - THE SEMI-CONTINUUM MODEL

We present gauge-origin independent calculations of the Cotton-Mouton effect of liquid water. The liquid is represented by a semi-continuum model such that the central molecule is surrounded by its first salvat ion shell, which explicitly accounts for the strong interaction betwee n the water molecule of interest and its closest neighbors. The long-r ange interactions with the solvent are modeled by a dielectric continu um surrounding the water molecule and the first solvation shell. We em ploy large basis sets, using London atomic orbitals in order to obtain gauge-origin independent results close to the Hartree-Fock limit. It is demonstrated that the direct interaction between neighboring molecu les leads to a large effect on the calculated Cotton-Mouton constant, which undergoes a sign change from the gas to liquid phase, as observe d previously for the linear electro-optical effect [K. V. Mikkelsen et al., J. Chem. Phys 102, 9362 (1995)]. Our best estimate for the molar Cotton-Mouton constant, -38.1.10(-20) G(-2) cm(3) mol(-1) (corrected for local field effects), is in reasonable agreement with the experime ntal value of -118(15).10(-20) G(-2) cm(3) mol(-1). We expect that the remaining discrepancy is mainly due to an inadequate treatment of ele ctron correlation. (C) 1998 American Institute of Physics.