The formation of specific clathrate hydrates and their transformation at given thermodynamic conditions depends on the interactions between the guest molecule/s and the host water lattice. Understanding their structural stability is essential to control structure‐property relations involved in different technological applications. Thus, the energetic aspects relative to CO2@sI clathrate hydrate are investigated through the computation of the underlying interactions, dominated by hydrogen bonds and van der Waals forces, from first‐principles electronic structure approaches. The stability of the CO2@sI clathrate is evaluated by combining bottom‐up and top‐down approaches. Guest‐free and CO2 guest‐filled aperiodic cages, up to the gradually CO2 occupation of the entire sI periodic unit cells were considered. Saturation, cohesive and binding energies for the systems are determined by employing a variety of density functionals and their performance is assessed. The dispersion corrections on the non‐covalent interactions are found to be important in the stabilization of the CO2@sI energies, with the encapsulation of the CO2 into guest‐free/empty cage/lattice being always an energetically favorable process for most of the functionals studied. The PW86PBE functional with XDM or D3(BJ) dispersion corrections predicts a lattice constant in accord to the experimental values available, and simultaneously provides a reliable description for the guest‐host interactions in the periodic CO2@sI crystal, as well as the energetics of its progressive single cage occupancy process. It has been found that the preferential orientation of the single CO2 in the large sI crystal cages has a stabilizing effect on the hydrate, concluding that the CO2@sI structure is favored either by considering the individual building block cages or the complete sI unit cell crystal. Such benchmark and methodology cross‐check studies benefit new data‐driven model research by providing high‐quality training information, with new insights that indicate the underlying factors governing their structure‐driven stability, and triggering further investigations for controlling the stabilization of these promising long‐term CO2 storage materials.

Through reliable first-principles computations, we have demonstrated the impact of CO 2 molecules enclathration on the stability of sI clathrate hydrates. Given the delicate balance between the interaction energy components (van der Waals, hydrogen bonds) present on such systems, we follow a systematic bottom-up approach starting from the individual 5 12 and 5 12 6 2 sI cages, up to all existing combinations of two-adjacent sI crystal cages to evaluate how such clathrate-like models perform on the evaluation of the guest-host and first-neighbors inter-cage effects, respectively. Interaction and binding energies of the CO 2 occupation of the sI cages were computed using DF-MP2 and different DFT/DFTÀ D electronic structure methodologies. The performance of selected DFT functionals, together with various semi-classical dispersion corrections schemes, were validated by comparison with reference ab initio DF-MP2 data, as well as experimental data from x-ray and neutron diffraction studies available. Our investigation confirms that the inclusion of the CO 2 in the cage/s is an energetically favorable process, with the CO 2 molecule preferring to occupy the large 5 12 6 2 sI cages compared to the 5 12 ones. Further, the present results conclude on the rigidity of the water cages arrangements, showing the importance of the inter-cage couplings in the cluster models under study. In particular, the guest-cage interaction is the key factor for the preferential orientation of the captured CO 2 molecules in the sI cages, while the inter-cage interactions seems to cause minor distortions with the CO 2 guest neighbors interactions do not extending beyond the large 5 12 6 2 sI cages. Such findings on these clathrate-like model systems are in accord with experimental observations, drawing a direct relevance to the structural stability of CO 2 @sI clathrates.

We performed first-principles computations to investigate guest-host/host-host effects on the encapsulation of the CO 2 molecule in sII clathrate hydrates from finite-size clusters up to periodic 3D crystal lattice systems. Structural and energetic properties were first computed for the individual and first-neighbors clathrate-like sII cages, where highly accurate ab initio quantum chemical methods are available nowadays, allowing in this way the assessment of the density functional (DFT) theoretical approaches employed. The performance of exchange-correlation functionals together with recently developed dispersion-corrected schemes was evaluated in describing interactions in both short-range and long-range regions of the potential. On this basis, structural relaxations of the CO 2 -filled and empty sII unit cells yield lattice and compressibility parameters comparable to experimental and previous theoretical values available for sII hydrates. According to these data, the CO 2 enclathration in the sII clathrate cages is a stabilizing process, either by considering both guest-host and host-host interactions in the complete unit cell or only the guest-water energies for the individual clathrate-like sII cages. CO 2 @sII clathrates are predicted to be stable whatever the dispersion correction applied and in the case of single cage occupancy are found to be more stable than the CO 2 @sI structures. Our results reveal that DFT approaches could provide a good reasonable description of the underlying interactions, enabling the investigation of formation and transformation processes as a function of temperature and pressure.

We performed first-principles computations to investigate the complex interplay of molecular interaction energies in determining the lattice structure and stability of CO 2 @sH clathrate hydrates. Density functional theory computations using periodic boundary conditions were employed to characterize energetics and the key structural properties of the sH clathrate crystal under pressure, such as equilibrium lattice volume and bulk modulus. The performance of exchange–correlation functionals together with recently developed dispersion-corrected schemes was evaluated in describing interactions in both short-range and long-range regions of the potential. Structural relaxations of the fully CO 2 -filled and empty sH unit cells yield crystal structure and lattice energies, while their compressibility parameters were derived by including the pressure dependencies. The present quantum chemistry computations suggest anisotropy in the compressibility of the sH clathrate hydrates, with the crystal being less compressible along the a -axis direction than along the c -axis one, in distinction from nearly isotropic sI and sII structures. The detailed results presented here give insight into the complex nature of the underlying guest–host interactions, checking earlier assumptions, providing critical tests, and improving estimates. Such entries may eventually lead to better predictions of thermodynamic properties and formation conditions, with a direct impact on emerging hydrate-based technologies.