Theoretical Background, Methods and Software

This chapter is devoted to the presentation of the computational methods used for the determination of the thermodynamic and the kinetic data of the compound considered in this work. We give in a first part a theoretical background of the methods used in the present work Electronic Structure Theory (ah initio, and Density Functional Theory), Statistical Mechanics theory. Group Additivity method, and multifrequency Quantum Rice-Ramsperger-Kassel theory (QRRK). 

The different software required to perform these computations are presented in a second part Gaussian, for the ah initio and Density Functional Theory calculations, SMCPS to perform the statistical mechanistics calculations, ThermKin and Chemaster for the kinetics calculations and THERM to apply the Group Additivity method. 

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This chapter is not aimed at describing the history of the application of semi empirical followed by ab initio molecular orbital methods in evaluating vibrational absorption intensities. There are a niunber of comprehensive review articles covering the early and later stages of these studies [21,52,53,168,169,173-176], We also do not intent to discuss details of the theoretical background of analytic derivative methods for calculations of intensities, also presented in excellent reviews [168,169,175], Our principal aim is to describe the current state-of-the-art in these calculations that are changing so frequently and so dramatically as a result of developments in computer technology, improved theoretical approaches or further perfectness in ab initio software. 

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