Scope of Computational Chemistry

Scope of Computational Chemistry--Computational chemistry scope covers various areas such as:

a. Molecular Dynamics

Containing molecular dynamics testing of the behavior of molecules or chemical system as a function of time, such as vibrational GERAKA or Brownian motion, this is often done with the explanation of classical mechanics are similar to the molecular mechanics calculations.

Application of molecular dynamics on the system solvent /solute allow calculation of system properties such as diffusion coefficient or radial distribution functions for use in the calculation of statistical mechanics. In general, the calculation scheme solvent / solute starts with a system consisting of a number of molecules with position and initial velocity. Energy from the newly calculated position relati to the previous position for a small time changes and the process is interacting greeting thousands of steps so that the system can be analyzed by taking samples of the system has reached equilibrium.

In order to analyze a single molecular vibration energy data Fourir transformed into the frequency domain. Given vibration peak can be selected and transformed into the time domain, so it can be seen what is causing the movement of the vibarasi frequency.

Molecular dynamics method is a simulation method which is very useful in studying the molecular systems such as organic molecules in solution and macromolecular compounds in the metabolic process. This method allows the depiction of the structure, thermodynamic properties and the dynamic nature of the system in the condensed phase. The principal part of the simulation methodology is the availability of an accurate potential energy function for modeling the properties of the system under study. The potential energy function can be prepared by methods of quantum mechanics Quantum mechanic, QM or molecular mechanics Molecular Mechanic, MM. The problem that arises is QM can only be used for simple systems with a few tens of unit mass given that QM calculations require a long time while the MM method is not sufficiently rigorous, to overcome this problem, developed a hybridization method known as the QM / MM, namely the critical of the system under study is calculated by the method of QM, while the system does not have to be explained in detail calculated by the method of MM. Methods QM / MM simulations are widely used in catalytic enzymatic reaction. Chemical processes in solution and docking of a protein in the receptor.

b. Statistical Mechanics

Statistical mechanics is a mathematical way to extrapolate thermodynamic properties of the material as a whole (proof) rests on a molecular picture of the level of paper and pencil method, because experts have not been able to resolve the quantum mechanics Schroedinger equation is an inexact until now so expert statistical mechanics does not have a starting point to develop completion method. Calculation of statistical mechanics is often done at the end of ab initio calculations of the properties of the gas phase. For condensed nature, often molecular dynamics calculations needed in order to conduct computational experiments.

One method that is widely used statistical mechanics in computational chemistry is Monte Carlo, with the Monte Carlo method, we can get an overview of the structure and the energy balance, but it can not provide a picture dynamics or properties that depend on time.

c. Solid state modeling

The electronic structure of the crystal structure of the ribbon defined by the plot plot bond structure, which gives the energy of molecular orbitals at each point in space, known as the area Bruillion Bruillion zone. Ab initio calculations and semiempiris produce orbital energy, so that they can be applied to band structure calculations, if the molecular energy calculation takes a long time, it will take far greater to calculate the energy of each point in the area Bruillion.

Band structure calculations have been done for a very complex system, however, the software automatically is not enough and not too quick to resolve cases of band structure.

d. Thermodynamics

Thermodynamics is one of the many explanations that have been constructed mathematical chemistry, thermodynamics treatment often obtained with paper and pencil work since many aspects of chemistry can be accurately described by a simple mathematical statement. Computational chemistry calculations will be able to assist the completion of the amount of thermodynamic calculations, would be very useful especially if we are dealing with large molecules.

Reference: Harno D Pranowo