Studies on the Microscopic Motion of a Diatomic in a Monatomic Solvent

Author: O'Brien, Edward Francis

Year: 1971

Degree: Master's thesis

Advisor: Robinson, G. Wilse

Committee Member: Unknown, Unknown

Option: Chemistry

DOI: 10.7907/JH9Y-QR36

Abstract

The microscopic motion of a diatomic in a monatomic solvent has been studied using the molecular dynamics method and a model of Lennard-Jones spheres for the monatomics and two such spheres joined by a rigid bond for the diatomic. Data were generated by computer for three systems, each at the same density but varying in temperature. From these data autocorrelation functions were calculated for the following random quantities of the motion of the diatomic: orientation of the diatomic, velocity of its center of mass angular velocity and momentum, mean square displacement of its center of mass and the forces on the diatomic bond. Infrared and Raman band shapes and NMR relaxation times were determined from the above correlation functions.

The decay times of the correlation functions were found to be in the range of 0.25 to 2.5 x 10^(-12) sec. The band shapes were symmetrical and their bandwidth change reflects the change in inhonaogeneous broadening with respect to temperature. The NMR, relaxation times also behave correctly with respect to temperature and indicate which of the relaxation mechanisms studied is dominant.

Further studies are proposed to determine the reason for the discrepancies between the above calculated quantities and those quantities obtained from experimental data.

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