What are the key factors governing the nucleation of CO2 hydrate?

Abstract

Microsecond molecular dynamics simulations were performed to provide molecular insights into the nucleation of CO₂ hydrate. The adsorption of sufficient CO₂ molecules around CO₂ hydration shells is revealed to be crucial to effectively stabilize the hydrogen bonds formed therein, catalyzing the hydration shells into hydrate cages and inducing the nucleation. Moreover, a high aqueous CO₂ concentration is found to be another key factor governing the nucleation of CO₂ hydrate, and only above a critical concentration can the nucleation of CO₂ hydrate occur. The 4¹5¹⁰6² cages, with size similar to the CO₂ hydration shell and an elliptical space closely matching a linear CO₂ molecule, play a dominant role in initiating the nucleation and remain the most abundant. The incipient CO₂ hydrate is rather amorphous due to the abundance of metastable cages (mostly 4¹5¹⁰6²).