Dear Manal,

Thanks for your immediate reply.  I have done that and it is showing different colours. What does they infer? kindly give me some clarifications

It is the map which shows the positive and negative reactivity centre of the molecule. One can globally know how the electron density cloud flow through all the atoms. In between group of positive and negative charges a potential is developed, there come the MEP

Dear Xavier,

Thanks for your answers. Can you give me more details about the MEp and what the colours suggests. How a MEP mapping helps in the reactivity of a molecule or in interpretting the vibrational spectrum of a compound?

Thank you manal, for your suggestions and answer. Your answer helped me alot in knowing about the MEP

Dear Venkatesan,

welcome,

I know that i came very late to your question but i find it fundamental and interesting. The electrostatic molecular potential results from its concentrated electric charges on its molecule, where positive charges are concentrated on the cation where negative charges concentrated on the anion. They form a sort of electric dipole. Every electric charge has surrounding to it its electric field. An electric field region has also an electrostatic potential.

The electric field E of a point charge Q is determined by the coulombs law:

E = Q/4pi epsilon0 r^2 , with r the distance of the point from the charge location.

The potential V whuch is the integration of the electric field from r= infinity to any point r, can be expressed by

V = Q/4pi epsilon0 r which is measured relative to r= infinity where it is assumed at this point V=0.

Therefore if we have positive charges, its potential will rise from zero at infinity and tends to very large values when r tends to zero. you use color scale to represent the potential ranges.

In case of negative charges the potential will be negative and reaches maximum negative at r=0.