Dielectric constant of ice Ih and ice V: a computer simulation study.
In this work, we exploit an efficient algorithm for the sampling of hydrogen-bond networks in order to study the order/disorder transition and the dielectric properties of ice Ih. Our results show that all of the rigid point charge models studied, TIP4P/Ice, TIP4P/2005, TIP4P, and SPC/E, yield a very low dielectric constant as compared with experiment. The analysis of the polarization factor, G, reveals that the structure of ice Ih as predicted by the TIP4P family of models studied is very similar. For all such models, G approximately 2.5, the differences in the dielectric constant being given mainly by the different molecular dipole moments. The angular correlations in the SPC/E model are very different, however, yielding G approximately 1.8. Our study suggests that the dielectric anisotropy of ice Ih is very small and at any rate smaller than the statistical uncertainty of our results. We show that for sufficiently anisotropic structures, such as ice V, the method employed does indeed reveal a strong anisotropy. At 5000 bar and 180 K, we find that the principal dielectric constants of ice V according to the TIP4P/Ice model are 34, 164, and 76. The order/disorder transition could not be well characterized, because of very strong hysteresis. Whereas low temperature ordered phases were readily disordered at temperatures below 50 K, the high temperature phase remained disordered upon cooling. Nevertheless, our plots of dielectric constant versus temperature reveal a clear lambda-like shape and obey a Curie-Weiss law. All of the models studied show a higher stability of the antiferroelectric Pna2(1) phase than the experimental ferroelectric Cmc2(1) phase.
MacDowell
Luis G
LG
Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040, Spain. luis@ender.quim.ucm.es
Vega
Carlos
C