Practical approaches of Quantum chemistry [part 2]

Anant Babu Marahatta
Ph.D. student in chemistry
Tohoku University

(Interested fellows are suggested to read the first part [Part 1] of this article before proceeding it).

In order to assist solving Schrödinger equations of the multi electron systems [referred as n body problems], Several Computers / Supercomputers with different mathematical software packages have been developed by applying the results of the theoretical chemistry [refer to an article “Computational chemistry” archived herewith].

By using the solution of the Schrödinger equations, these calculating packages generate information such as properties of molecules and simulate the experimental results. For instance, we can calculate:

electronic structure determinations [(i.e. the expected positions of the constituent atoms)]
• dipoles and higher multipole moments

• absolute and relative (interaction) energies
• geometry optimizations [the lowest energy and the most stable form]
• frequency calculations [ vibrational and other spectroscopic quantities]
• migrating mechanisms of the active groups
• Dynamics of the molecular rotor, gyroscope, brake, motor etc.
transition structures
protein calculations

Here is the video of chaperonin [example of protein] transition from open to closed conformation *.
• reaction mechanisms
• cross sections for collision with other particles
• electron and charge distributions
potential energy surfaces (PES) **

• rate constants for chemical re actions (kinetics)
• Thermodynamic calculations- heat of reactions, energy of activation etc.
• NMR Calculations etc.
The Computational quantum chemistry methods which range from highly accurate to very approximate techniques will be clarified on part 3.

*Booth et al., 2008 - www.nature.com
**Johnson et al., Chemical & Engineering News (vol.80, No. 2, 2002)

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