Interactive computer graphics in quantum chemistry research

Abstract

The broad aim of this thesis is to investigate the feasibility of using interactive computer graphical methods to control experiments in scientific research. A particular area of scientific research, namely quantum chemistry, is chosen because within it the widely used semi-empirical methods provide an excellent framework, from both theoretical and practical points of view, upon which to base the investigation.
The first chapter discusses interactive computer graphics in general terms, and reviews the origin, development and a few significant applications of graphical techniques, before briefly considering some aspects of hardware, software and graphics systems design.
In the second chapter the specific advantages which graphical techniques offer in scientific work are examined against the background presented in chapter one. Then, after reviewing the nature of the chosen problem area and the conventional role of
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the computer, attention is turned to the question of designing a graphics system for use in quantum chemistry research.
The third chapter describes in detail an experimental yet comprehensive system developed for this purpose on an ICL 4130 computer equipped with a graphical display device. The design of the system is related to the typical problem-solving phases used in many areas of scientific work, but which are particularly well defined in the chosen area of quantum chemistry. The system also takes advantage of the many opportunities for graphical displays presented in each of the phases so defined. The form of control adopted is through a ’menu’ type of dialogue, where at each decision point in the course of an interactive session, a list of available options is displayed to the user. Selection is then made by light pen, console key or typewriter keyboard.
The fourth and fifth chapters describe practical experiments
with the graphics system, dealing with properties of SCF ground
* , . states and excited states respectively.
The sixth and seventh chapters contain theoretical studies of phosphonitrilic polymers which emerged partly from a consideration of extending the range of applications to molecular systems beyond the ’standard' molecules with well-known properties which are used for designing and illustrating the graphics system in the earlier chapters. The concept of the 'island' orbital in such molecular systems is discussed in detail at both the Huckel and SCF-CI levels of approximation, and the analysis finally leads to conclusions regarding the influence of island orbital solutions on the UV spectrum.