The Thermodynamic and Ground State Properties of the TIP4P Water Octamer

Authors

E. Asare
A-R. Musah
E. Curotto
David L. Freeman, University of Rhode IslandFollow
J. D. Doll

Document Type

Article

Date of Original Version

11-13-2009

Department

Chemistry

Abstract

Several stochastic simulations of the TIP4P [W. L. Jorgensen, J. Chandrasekhar, J. D. Madura, R. W. Impey, and M. L. Klein, J. Chem. Phys. 79, 926 (1983)] water octamer are performed. Use is made of the stereographic projection path integral and the Green’s function stereographic projection diffusion Monte Carlo techniques, recently developed in one of our groups. The importance sampling for the diffusion Monte Carlo algorithm is obtained by optimizing a simple wave function using variational Monte Carlo enhanced with parallel tempering to overcome quasiergodicity problems. The quantum heat capacity of the TIP4P octamer contains a pronounced melting peak at 160 K, about 50 K lower than the classical melting peak. The zero point energy of the TIP4P water octamer is 0.0348± 0.0002 hartree. By characterizing several large samples of configurations visited by both guided and unguided diffusion walks, we determine that both the TIP4P and the SPC [H. J. C. Berendsen, J. P. Postma, W. F. von Gunsteren, and J. Hermans, (Intermolecular Forces, Reidel, 1981). p. 331] octamer have a ground state wave functions predominantly contained within the D_2d basin of attraction. This result contrasts with the structure of the global minimum for the TIP4P potential, which is an S₄ cube. Comparisons of the thermodynamic and ground-state properties are made with the SPC octamer as well.

Citation/Publisher Attribution

Asare, E., Musah, A.-R., Curotto, E., Freeman, D. L., & Doll, J. D. (2009). The Thermodynamic and Ground State Properties of the T1P4P Water Octamer. Journal of Chemical Physics, 131(18), 184508. doi: 10.1063/1.3259047

Available at: http://dx.doi.org/10.1063/1.3259047

Publisher Statement

© 2009 American Institute of Physics.