Computational density-functional approaches on finite-size and guest-lattice effects in CO₂@sII clathrate hydrate

We performed first-principles computations to investigate guest–host/host–host effects on the encapsulation of CO2 molecule in sII clathrate hydrates from finite-size clusters up periodic 3D crystal lattice systems. Structural and energetic properties were first computed for individual first-neighbors clathrate-like cages, where highly accurate ab initio quantum chemical methods are available nowadays, allowing this way assessment density functional (DFT) theoretical approaches employed. The performance exchange–correlation functionals together with recently developed dispersion-corrected schemes was evaluated describing interactions both short-range long-range regions potential. On basis, structural relaxations CO2-filled empty unit cells yield compressibility parameters comparable experimental previous values hydrates. According these data, enclathration cages is a stabilizing process, either by considering guest–host host–host complete cell or only guest–water energies cages. CO2@sII clathrates predicted be stable whatever dispersion correction applied case single cage occupancy found more than CO2@sI structures. Our results reveal that DFT could provide good reasonable description underlying interactions, enabling investigation formation transformation processes as function temperature pressure.