THEORETICAL CHEMISTRY

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 1: Main sub-branches of Theoretical Chemistry

CHEMICAL BONDING & ELECTRONIC STRUCTURE	STATISTICAL MECHANICS	REACTION DYNAMICS
Lewis Theory of Bonding	Quantum Statistics	Adiabatic
Valence Bond Theory	Boltzmann Average	Intermolecular
Molecular Orbital Theory	Partition Functions	Intramolecular
Covalent Bond Distance	Correlation Functions	Information Theory
Computational chemistry	Ensembles	Kinematics
Ab initio calculations	Pair Distribution Functions	Molecular Dynamics
Semi-empirical calculations
Modern Valence Bond
Generalized Valence Bond
Quantum Chemistry
Quantum Monte Carlo
Molecular Modelling
Molecular Mechanics
Cheminformatics

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.

 

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

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.