# Question on vashishta potential

Dear LAMMPS users,

Hi,

In the vashishta potential, LAMMPS needs the parameter D to be in evA^4. However, in papers it is usually reported in eA^6. Sorry to ask, but could you please elaborate on the appropriate conversion ?

Thanks,

Ali

Vashishta has a series of potential parameters, so could you tell us which one you are referring to? There is no conversion for what you are referring to here, so just check the functional form and make sure that the parameter you put in for the 1/r^4 term is D (or possibly D/2 depending on another factor in the denominator).

Anders

Hi Anders,

As you may know, D = (alphaiZj^2+alphajZi^2)/2. Since, alpha is in A^3 unit and Z is in e unit, the whole unit would be e^2Z^3. However if you go through Vashishta files, it needs D to be in evA^6. By the way, I just found that e^2/A = 14.39 ev and this is the conversion that I was looking for. Anyway, I really appreciate your help.

Thanks,

Ali

.

Yep, I totally agree. Glad you figured it out!

Anders