Chemistry Net: Physical & Theoretical Chemistry

Physical & Theoretical Chemistry

Physical & Theoretical Chemistry















Theoretical chemistry is a diverse field of chemistry that uses physics, mathematics and computers to help us understand molecular behavior, to simulate molecular phenomena, and to predict the properties of new molecules. It is common to hear this discipline referred to as theoretical and computational chemistry.

The advent of computers and the development of software which is increasingly easy to use has revolutionized the approach toward understanding chemistry at a fundamental level and an increase is observed in the number of people interested in theoretical and particularly in computational chemistry.

The term computational chemistry is usually used when a mathematical method is sufficiently well developed that it can be automated for implementation on a computer. Computational chemistry / molecular modeling is therefore the science of representing molecular structures numerically and simulating their behavior with the equations of quantum and classical physics. Computational chemistry programs allow scientists to generate and present molecular data including geometries (bond lengths, bond angles), energies (activation energy, heat of formation), electronic properties (charges, ionization potential, electron affinity), spectroscopic properties (vibrational modes, chemical shifts) and bulk properties (volumes, surface areas, diffusion, viscosity). Over the past ten to twenty years, scientists have used computer models of new drugs to help define biological activity profiles, geometries and reactivities.

Theoretical chemistry may be broadly divided into electronic structure and chemical bonding, reaction dynamics, and statistical mechanics.


 Table I.1: Main sub-branches of Theoretical Chemistry


Chemical Bonding & Electronic Structure lies at the very core of Chemistry. It is what enables about one-hundred elements to form millions of chemical substances. Main sub-branches are: Lewis theory of bonding, valence bond theory, molecular orbital theory, covalent bond distance, computational chemistry, ab initio calculations, semi-empirical calculations, modern valence bond theory, generalized valence bond, quantum chemistry, quantum Monte Carlo, molecular modelling, molecular mechanics, cheminformatics.


Reaction dynamics is a field of chemistry, studying why chemical reactions occur in gases, in liquid, at interfaces and how to predict their behavior and how to control them. The main objectives of reaction dynamics are:

  • The microscopic foundation of chemical kinetics
  • State to state chemistry and chemistry in real time
  • Control of chemical reactions at the microscopic level

Main sub-branches are: Adiabatic, intermolecular, intramolecular reaction dynamics, information theory, kinematics, molecular dynamics.


Statistical mechanics sets out to explain the behavior of macroscopic systems by studying the statistical properties of their microscopic constituents. Applications of the techniques of statistical mechanics include:

  • Applications to physical systems such as solids, liquids and gases
  • Applications to colloids, interfaces, polymers and biopolymers.

Main sub-branches are: Quantum Statistics, Boltzmann average, partition functions, correlation functions, ensembles, pair distribution functions.



  1. P. Atkins, J de Paula,  “Physical Chemistry: Thermodynamics, Structure and Change”, 10th Edition, W. H. Freeman, 2014
  2. D. A. McQuarrie, J. D. Simon,“Physical Chemistry: A Molecular Approach”, 1st Edition, University Science Books, 1997
  3. K. J. Laidler, J.H. Meiser, B.C. Sanctuary, “Physical Chemistry”, 4th Edition, Brooks Cole, 2002
  4. J. Simons, "An Introduction to Theoretical Chemistry", 1st Edition, Cambridge University Press, 2003

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