First-principles study of water confined in single-walled silicon carbide nanotubes

In the present work, water molecules confined inside single-walled silicon carbide nanotubes (SiCNTs) are studied using density functional theory calculations. A set of periodic boundary condition models are established for segments of single-file water chains, infinite single-file water chains, and infinite multifiled water networks encapsulated within the periodic armchair and zigzag SiCNTs with (5,5), (6,6), (8,0), (9,0), and (10,0) chiralities. Two hybrid density functionals with and without dispersion correction, ωB97XD and B3LYP, respectively, are employed in all calculations for structure, interaction energy, and charge analysis. Although the silicon carbide surface is essentially hydrophilic, water molecules within SiCNTs have structures and properties that resemble those in the hydrophobic single-walled carbon nanotube since both are controlled by the geometry confinement. It is necessary to include dispersion corrections to describe the weak interactions between the water molecules and the SiCNT wall which arise mainly from van der Waals interactions and a slight charge transfer from SiCNT to the enclosed water molecules.