Diffusion Monte Carlo characterization of a methane molecule in a (H$_{2}$O)$_{20}$ dodecahedral cage

The interaction energy of a methane molecule encapsulated in a dodecahedral water cage is calculated using the MP2, MP2C, various dispersion-corrected DFT, and diffusion Monte Carlo (DMC) methods. The MP2, MP2C, and DMC methods give binding energies of −5.04, −4.60, and −5.3 ± 0.5 kcal/mol, respectively. In addition, the two- and three-body contributions are evaluated using the DFT, MP2, and CCSD(T) methods. All of the DFT methods considered appreciably overestimate the magnitude of the three-body contribution to the interaction energy. The two- and three-body energies are further analyzed by use of symmetry-adapted perturbation theory (SAPT) which allows decomposition into electrostatics, exchange, induction, and dispersion contributions. The SAPT calculations reveal that the induction, dispersion, and exchange three-body contributions to the methane-cage binding energy are all sizable, with the net three-body contribution to the binding energy being about 1 kcal/mol.

Journal of Physical Chemistry C, 2019

The journal of physical chemistry. A, 2013

The quantum Monte Carlo method is used to calculate the binding energy of an (H2O)16 cluster that has been the subject of several recent theoretical studies. The resulting interaction energy, -165.1(8) kcal/mol, is very close to our MP2 complete basis set limit interaction energy of -164.1 kcal/mol. Comparison of these results with those for the one-, two-, three-, and four-body interaction energies leads us to conclude that the five- and higher-body interactions are attractive, contributing over 2 kcal/mol to the net interaction energy of this (H2O)16 isomer.

Theoretical Chemistry Accounts, 2012

The Journal of Physical Chemistry C, 2009

Chemical Reviews, 2014

Physical Chemistry Chemical Physics, 2012

Molecular Simulation, 2019

2016

● Concept of Curriculum Change ● Elements of successful Curriculum Change ● Factors affecting Curriculum change ● Role of students, teachers and educational administrators in Curriculum Change.