Simulations of proton order and disorder in ice Ih

Abstract

Computer simulations of ice Ih with different proton orientations are presented. Simulations of proton disordered ice are carried out using a Monte Carlo method which samples over proton degree of freedom, allowing for the calculation of the dielectric constant and for the examination of the degree of proton disorder. Simulations are also presented for two proton ordered structures of ice Ih, the ferroelectric Cmc2 1 structure or ice XI and the antiferroelectric Pna2 1 structure. These simulations indicate that a transition to a proton ordered phase occurs at low temperatures ͑below 80 K͒. The symmetry of the ordered phase is found to be dependent on the water potential. The stability of the two proton ordered structures is due to a balance of short-ranged interactions which tend to stabilize the Pna2 1 structure and longer-range interactions which stabilize the Cmc2 1 structure.

Two-dimensional infrared spectroscopy of isotope-diluted ice Ih

“…14 One of the intriguing variations among the crystalline forms is that in some cases protons are randomly distributed in an otherwise regular oxygen lattice, following the ice rules. [15][16][17] Ice Ih, one of these disordered forms, is the stable crystalline ice under ambient pressure within the temperature range of 273 K to 72 K. Lower in temperature lies its proton ordered counterpart, ice XI. [18][19][20][21] Proton disorder is interesting from a theoretical point of view, considering the possible impact it has to the phonon and exciton dynamics of ice Ih.…”

Proton disorder and the dielectric constant of type II clathrate hydrates

“…• Given the known sensitivity of the calculated dielectric constant of Ih ice to the model potential used, 33 what is the sensitivity of the ratio of the ice to clathrate dielectric constants to model potential?…”

“…Rather, the differing hydrogen bond arrangements depend on the orientation of the hydrogen bonded dimer, 30 as well as the interactions from other neighbors. [31][32][33] For the kind of dimers that make up a type sII clathrate, there are two possible dimer orientations, which can be labeled inverse mirror ͑IM͒ or oblique mirror ͑OM͒ ͑see Fig. 1͒.…”

“…2 Computer simulations can sample, in principle, all relevant proton configurations using a Monte Carlo method in which many particle moves are attempted between different structures that all obey the ice rules. 33,[39][40][41][42] This method has been applied to calculate the dielectric constant and proton order parameters for ice Ih. 33,42 In this study, this method will be used to examine type II clathrates with different guests.…”

“…33,[39][40][41][42] This method has been applied to calculate the dielectric constant and proton order parameters for ice Ih. 33,42 In this study, this method will be used to examine type II clathrates with different guests. The goal of this work is to find answers to the following questions:…”