Hexagonal and Cubic Ice at Low Temperatures

Formation of hexagonal and cubic ice during low-temperature growth.

From our daily life we are familiar with hexagonal ice, but at very low temperature ice can exist in a different structure--that of cubic ice. Seeking to unravel the enigmatic relationship between these two low-pressure phases, we examined their formation on a Pt(111) substrate at low temperatures with scanning tunneling microscopy and atomic force microscopy. After completion of the one-molecu...

Proton ordering in cubic ice and hexagonal ice; a potential new ice phase--XIc.

Ordinary water ice forms under ambient conditions and has two polytypes, hexagonal ice (Ih) and cubic ice (Ic). From a careful comparison of proton ordering arrangements in Ih and Ic using periodic density functional theory (DFT) and diffusion Monte Carlo (DMC) approaches, we find that the most stable arrangement of water molecules in cubic ice is isoenergetic with that of the proton ordered fo...

Properties of a Statistical Model of Ice at Low Temperatures

A simple statistical model for ice is presented, based on a point charge model for H2O. To simulate this model, a Monte Carlo algorithm is constructed that samples proton configurations according to the Boltzmann distribution. The ground state of the model is numerically found to be an ordered nonferroelectric state with a unit cell of eight water molecules. The same structure has been previous...

Interactions of adsorbed CO₂ on water ice at low temperatures.

We present a computational study into the adsorption properties of CO2 on amorphous and crystalline water surfaces under astrophysically relevant conditions. Water and carbon dioxide are two of the most dominant species in the icy mantles of interstellar dust grains and a thorough understanding of their solid phase interactions at low temperatures is crucial for understanding the structural evo...

Freezing Properties of Disaccharide Solutions: Inhibition of Hexagonal Ice Crystal Growth and Formation of Cubic Ice