# Solvent effect evaluation

## Existing Calculation methods

- such as Monte Carlo (MC) simulations and Molecular Dynamics (MD) calculations
have been using for calculation of difference in free energy of solvations.
- Use classical force fields depending on specific parameters such as van der Waals parameters and charges for solvent molecules as well as solute molecules, especially TS.

## The QM/MC simulations

- calculate energies of ensembles by use of
**Quantum Mechanical (QM)** calculations,
- are free from classical force fields,
- can analyze interactions among solvents and the solute,
- requires long CPU times to obtain energies with statistical meanings.
- are extended to calculate difference in free energy of solution using the free energy perturbation (FEP) method, i.e., QM/MC/FEP method.

**Disadvantages of QM/MC/FEP methods**

- 40,000-100,00 energies are required to obtain results with statistical
meanings. It means the methopd need large demands of computational power
so that we have to parallelize the program.
- Sizes of droplets are limitted because of computer powers we have. We have
to check size dependency of the results