Fragmentation of Charged Binary Clusters

Fragmentation of binary mesoscopic clusters composed of H2O/CH3OH and charged with ions (Na+, K+, Cs+,F^, Cl-, I-) of similar sign are studied by molecular simulation. The fragmentation involves the departure of a cluster containing one or more ions from the parent droplet by a break-down of the non-covalent interactions of the solvent. The fragmentation occurs because of the high charge of the droplet. The molecular mechanism of fragmentation is examined by the theories relating to activated processes. Free energy profiles are built along the course of the fragmentation event by following the process with a novel reaction coordinate. This reaction coordinate is named transfer reaction coordinate (TRC) and includes the positional degrees of freedom of all the solvent molecules and ions in its construction. It is very sensitive to the location of the ions, and many tests show that it can successfully distinguish configurations that correspond to the barrier top of the free energy profile. These configurations finally determine the dynamics of the fragmentation process and, therefore, the rate of the process. In this research, the behaviour of the ions in the clusters is characterized by a variety of static quantities such as radial distribution func tions, radial density functions, and solvation number, as well dynamic quantities such as solvent residence correlation functions and mean square displacement. Only uneven frag mentation is observed at 200K. However, both even and uneven fragmentation are observed at 300K. In clusters composed of 100%H2O, uneven fragmentation results in distinct prod uct distributions characteristic of the nature of the solvation of each ion. This is not the case for methanol. The transition state in methanol does not retain any solvation characteristics of the fragmenting ion and occurs much closer to the main body of the droplet. The free energy barrier decreases drastically with methanol content at 200K. In binary systems, the positive ions fragment both evenly and unevenly with slightly more methanol than the neg ative ions. At 300K, uneven fragmentation is found to be the predominant reaction channel, iii However, even fragmentation is more prominent in binary systems

Name thesis:degree_name

M Sc

Discipline thesis:degree_discipline

Chemistry

Grantor dc:publisher

The University of Western Ontario

Year dc:date.issued

2006

Author dc:creator

• Mainer, Kirkland Roy

Advisor dc:contributor.advisor

• Constas, Styliani

• fragmentation reactions
• binary clusters
• computer simulations
• activated pro cesses
• transfer reaction coordinate
• potential of mean force
• charged clusters.

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/20.500.14721/38578

OAI identifier oai:identifier

oai:uwo.scholaris.ca:20.500.14721/38578