title: Electronic structure, molecular interaction, and stability of the CH4-nH2O complex, for n = 1-21.
abstract: Molecular calculations were carried out with four different methodologies to study the CH 4- nH 2O complex, for n = 1-21. The HF and MP2 methods used considered the O atom with pseudopotential to freeze the 1s shell. The other methodologies applied the Bhandhlyp and B3lyp exchange and correlation functionals. The optimized CH 4- nH 2O structures are reported, specifying the number and type of H 2O subunits (triangle, square, pentagon, etc.) that comprised the nH 2O counterpart cluster or cage, that interacted with the CH 4 molecule, and, in the latter case, that provided its confinement. Results are focused to understand the stability of the CH 4- nH 2O complex. The quality of the electron correlation effect, as well as the size of the nH 2O cage to confine the guest molecule, and the number and type of H 2O subunits comprising the nH 2O cluster or cage are the most important factors to provide the stability of the complex and also dictate the particular n value at which the CH 4 molecule confinement occurs. This number was 14 for the HF, Bhandhlyp, and B3Lyp methods and 16 for the MP2 method. The reported hydrate structures for n < 20 could be predictive for future experiments.
authors: Programa de Ingeniería Molecular, Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, 07730 México D. F., Mexico. gbperez@imp.mx
authors: Graciela
authors: G
authors: Bravo-Pérez
authors: Armando
authors: A
authors: Cruz-Torres
authors: Ascención
authors: A
authors: Romero-Martínez
mesh_terms: D003198:Computer Simulation; D004583:Electrons; D008697:Methane / Q000737:chemistry*; D008956:Models, Chemical; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D008697:Methane