Numerical Studies on Surplus Electrons in Polar Media

Carmichael, Ian C (1974) Numerical Studies on Surplus Electrons in Polar Media. PhD thesis, University of Glasgow.

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Abstract

Accurate numerical solutions of the polarized cavity and semicontinuum models for excess electrons in polar media are derived. Part I presents the results of a numerical investigation of similar models for the surplus electron in crystalline solids. Here, the existence of a few analytical and numerical solutions affords an excellent check on the accuracy and efficiency of the presently-used finite-difference technique. In addition, the extent of amelioration produced in approximate variational treatments is disclosed. Some relevant theory is developed. In Part II the numerical technique is used in a thorough-going study of polarized cavity and semicontinuum models, within both the adiabatic and scf formulations, for the excess single-electron species. The considerable improvements effected on existing one-parameter variational approaches is demonstrated and several results are called into question. In particular the scf treatment of the polarized cavity model for the hydrated electron is shown to be inadequate. This refutes a recent, variationally-based claim to the contrary. In the realm of semicontinuum theories it is shown that the presently used parameterizations do, on accurate solution, no longer give concurrence with experimental data. While this could be renewed for any given observation by a more appropriate selection of variables, deviations will generally remain in the other predictions. It is shown to be unlikely that transitions to higher excited states contribute much to the observed band width, which the present treatments based on a single 1s-2p transition badly underestimate. Localized dielectron species form the subject of Part III. The numerical solution technique is carried through on similar levels of approximation in an attempt to resolve recent contradictory statements as to the dissociative stability of the ammoniated dielectron made by the alternative formulations of the semicontinuum model. The disparity remains. The introduction of a second solvation shell is effected in an attempt to reduce the computational differences of the models used, but to no avail. The adiabatic treatment prefers two singly-solvated species while an scf scheme favours a trapped dielectron. Absorption at doubly-charged sites is shown to be of doubtful importance in the observed spectrum. Clearly some major alterations in the present models are necessary. The contradiction has now been removed. More recent calculations have revealed that, within the semicontinuum model, the adiabatic approximation also favours stable dielectrons.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Physical chemistry, Computational chemistry
Date of Award: 1974
Depositing User: Enlighten Team
Unique ID: glathesis:1974-78672
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:04
Last Modified: 30 Jan 2020 15:04
URI: http://theses.gla.ac.uk/id/eprint/78672

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