this letter, a possible reason behind selective host-guest organization in the initial stage of sI methane hydrate nucleation is provided, through density functional theory based calculations. In doing so, we have connected earlier experimental and theoretical observations on the structure and energetics of sI methane hydrate to our findings. Geometry and relative stability of small (H2O)(5) and (H2O)(6) clusters, presence of CH4 guest, integrity and cavity radius of (H2O)(20) and (H2O)(24), as well as the weak van der Waals type of forces, particularly dispersion interaction, are major factors responsible for initial formation of methane encapsulated dodecahedron cavity over tetrakaidecahedron. (C) 2017 Elsevier B.V. All rights reserved.