Dear admins,
I'm trying to develop a MLFF for amorphous Si. I performed on-the-fly training, followed by a refit calculation to generate MLFF. The number of configurations is 1629, and number of basis sets is 6784. From ML_LOGFILE for the refit calculation, the error in energy is 10.3 meV/atom and error in force is 0.15 eV/Angstrom.
Using the generated MLFF, I run an MD of amorphous Si. From the trajectory of the simulation, I selected 50 configurations. For each configuration, I performed single point DFT and MLFF calculations, based on which the mean absolute error and max error were calculated. The mean absolute error in energy is 10.6 meV/atom and in force is 0.14 eV/Angstrom, which seems to be consistent with those from the refit calculation. However, the max error in energy is 28.6 meV/atom, and 0.92 eV/Angstrom in force.
So my questions are:
1) The max error in energy and in force are much larger than the mean. For sure max error will be larger, but in my case the max error in force is almost 7 times larger than the mean - is this behavior normal? Can I trust the result from the MLFF? If not, any suggestions on how to minimize the max error?
2) VASP manual recommend an energy error of less than 1 meV/atom and force error of less than 0.1 eV/Angstrom. The errors I have are beyond those recommended values. Since I'm modeling amorphous materials, I guess a larger error is expected. What are typically errors for amorphous materials? Do you have any recommendation on how to minimize the training error?
3) I have 1629 configurations and 6784 local references. Are those numbers reasonable for amorphous materials?
Any insights will be greatly appreciated. Thank you very much.