If the Lennard-Jones potential function is used for multibody calculations, if the values of \epsilon and \sigma are set differently in different types of atoms, does it mean that the approximation units of these two are not the same in different type atoms interaction.
Then the result of the calculation using dynamical_matrix is unable to use the eskm type due to the use of LJ units, but I now need to convert the units to THz. How do I go about doing this?
Thank you for your help!
Don’t do your calculations in LJ units!
When you want regular units in your results, use regular and not reduced units in your simulation.
Reduced units are useful when you want to derive results that are independent of the underlying material, but a major pain, if you do want to set the material and thus ultimately need to “unreduce” your units.
Thank you for your answer.
But there is still a question that has been bothering me, if for different atom type settings of \epsilon
and \sigma, does it mean that the reduced units between them is different.
For example, the reduced units between 1-1 atom types would have to be chosen as \epsilon_{11} and \sigma_{11}, while the 1-2 atom types are \epsilon_{12} and \sigma_{12}
There are several detailed discussions about how reduced units work in the archives. Please have a look.
Also check out: units command — LAMMPS documentation
and the appendices of Allen and Tildesley, Computer Simulation of Liquids, Oxford University Press (1987)