[lammps-users] Reference for values of constants in the LJ unit system

Hi everyone,

Is anyone familiar with any reference referring to the derivation of the LJ unit system in LAMMPS? More specifically, I need to figure out how the values of the de Broglie wavelength and Planck’s constant are derived in that unit system (how exactly they follow from assuming unit length, unit energy, and unit Boltzmann constant).

Thank you beforehand for any reference you may be able to point me to,

why don’t you run your simulations in real or metal units where this would not be a problem?

Because I’m post-processing datasets generated in LJ.

same difference. convert length, energy, mass, etc. to your desired units for the material in question and then this becomes a non-issue.

I don’t know if you can actually do this conversion in reduced units directly without knowing the material and thus having a reference for the “real” values.
e.g. since the planck constant is a fixed value in non-reduced energy and time units you will need to know what your energy, mass and length unit in non-reduced units are, to relate to it. those three properties are essentially independent in reduced units and you can freely choose which you use as a reference to reduce your values by.

See Allen & Tildesley, Computer Simluation of Liquids, Appendix B, 1989.


I’ll try Alex’s tip and search for the book Steve recommended. Thank you very much to both of you!!!