



Computational chemistry is rapidly emerging as a subﬁeld of theoretical chemistry, where the primary focus is on solving chemically related problems by calculations.
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 is the application of chemical, mathematical and computing skills to the solution of interesting chemical problems. It uses computers to generate information such as properties of molecules or simulated experimental results.
The quantum and classical mechanics as well as statistical physics and thermodynamics are the foundation for most of the computational chemistry theory and computer programs. This is because they model the atoms and molecules with mathematics. Using computational chemistry software the following can be performed:
 electronic structure determinations
 geometry optimizations
 frequency calculations
 definition of transition structures and reaction paths
 docking in protein calculations
 charge and electron distributions calculations
 calculations of potential energy surfaces (PES)
 calculations of rate constants for chemical reactions (kinetics) thermodynamic calculations heat of reactions, energy of activation
 calculation of many other molecular and physical and chemical properties.
Computational chemistry is therefore one of the most fascinating branches of theoretical chemistry that is useful in resolving many chemical problems. It comprises of a wide variety of techniques and methods developed over the last century such as:
abinitio (Latin for "from the beginning") a group of methods in which molecular structures can be calculated using nothing but the Schrödinger equation, the values of the fundamental constants and the atomic numbers of the atoms present.
semiempirical use approximations from empirical (experimental) data to provide the input into the mathematical models.
molecular mechanics uses classical physics and empirical or semiempirical (predetermined) force fields to explain and interpret the behavior of atoms and molecules.
Computational chemistry has become a useful way to investigate materials that are too difficult to find or too expensive to purchase. It also helps chemists make predictions before running the actual experiments so that they can be better prepared for making observations.
"I would like to emphasize my belief that the era of computing chemists, when hundreds if not thousands of chemists will go to the computing machine instead of the laboratory, for increasingly many facets of chemical information, is already at hand. There is only one obstacle, namely, that someone must pay for the computing time. " [Robert S. Mulliken (18961986), at the end of his Nobel address in 1966]
References
 F. Jensen. “Introduction to Computational Chemistry”, 2nd Edition, Jon Wiley and Sons Ltd., 2007
 S. M. P. Bachrach "Computational Organic Chemistry", Jon Wiley and Sons Ltd., 2007
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