STSM by Daniel Jose Arismendi Arrieta, Institute of Fundamental Physics (IFF-CSIC), Madrid (ES) with Graham Worth, University of  Birmingham (UK)
On February 3rd, 2014 (90 days)ARIS_logo
From SPAIN to UNITED KINGDOM

Confining molecules inside a nanoscale cavity: the case of clathrate hydrates

In order to provide insights into the water-trapped gas interactions, active research using simulations for hydrates continues to make progress in quantifying spectroscopic values, growth rates, thermodynamic stability, and other physical properties. They have been found to occur naturally in large quantities, and have important industrial applications. The interest in CO2 hydrate is driven in part by the possibility of its storage replacing and extracting of methane trapped in deep ocean clathrates, as well as due to its interest in astrophysics and its formation conditions at Mars, satellites, comets and dense interstellar clouds.

From the perspective of quantum dynamics, by confining a molecule into a cage leads to the quantization of the translational (T) degrees of freedom of its center of mass, and well as to its rotational (R) and vibrational (V) states. This allows the investigation of the dynamics of the guest molecule, and the effect of the size, shape and composition of the host cavity, as well as the occupancy and identity of the trapped molecules, and finally the validation of model interactions. Between several methods to describe the time-evolution of a chemical system at the atomic level by directly solving the Schrödinger equation, the most versatile and efficient is probably the multi-configuration time-dependent Hartree (MCTDH) method.

In this STSM, most of the work was invested on deriving the Hamiltonian setup for treating efficiently the full-dimensional system (e.g. triatomic molecule inside of hydrate cavity types) within the MCTDH program. The next step is to conclude and prepare the analysis of results for a publication. We stablish a new collaboration with the MCTDH developers in Birmingham and for future collaborations such system will be used as a benchmark calculation for direct dynamic methods.

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The VCO2−cavity interaction potential as a function of distance R between the center of mass of the cavity and the center of mass of the CO2 molecule. Zero point energies are with their corresponding geometries are shown for the small (512) and large (51262 ) cavities of SI clathrate structure. The small cavity (512) is common to all structures clathrate structures.

 

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