Molecular dynamics study on desublimation and crystal nucleation of carbon dioxide on a low temperature surface

Abstract

To capture CO2 crystal nucleation during the desublimation, we conducted a molecular dynamics study on the desublimation process of CO2 on a low temperature plate. The desublimation process is characterized by three models corresponding to different degrees of supercooling. When the plate temperature is below 82 K, the solid CO2 with a glassy state structure forms after CO2 gas molecules adsorb onto the cool plate. In the temperature range of 83–113 K, CO2 crystal nucleus forms within the disordered solid CO2, and subsequently the nucleus grows into Pa3-type crystal. For the plate temperature between 114 and 128 K, a liquid CO2 phase initially forms, the nucleus then generates and grows to develop into Pa3 crystal. The CO2 crystal nucleation is accompanied by the reduction of molecular potential energy and the increase of molecular kinetic energy. Additionally, the recalescence phenomenon occurs during CO2 crystal nucleation. It is crucial that the molecular kinetic energy and molecular distance fall within a specific range to enable the formation of CO2 nucleus and regular Pa3 crystal. Consequently, the CO2 crystal nucleation can only occur within a specific range of plate temperatures.