Hello, I am an undergrad research intern looking to understand how to use lammps to simulate femtosecond laser ablation and am still learning about md and lammps. I found a paper (Mareev et al.) which uses fix ttm/mod to simulate ablation of Si and they have listed the values of the parameters used in the paramater file for fix ttm/mod:
Mareev, E., Pushkin, A., Migal, E., Lvov, K., Stremoukhov, S., & Potemkin, F. (2022). Single-shot femtosecond bulk micromachining of silicon with mid-IR tightly focused beams. Scientific reports , 12 (1), 7517. Single-shot femtosecond bulk micromachining of silicon with mid-IR tightly focused beams | Scientific Reports
I also found Professor Kohlmeyer’s sample fix ttm/mod code on gitlab which also uses Si. However, the parameters in the input files from Mareev et al. and the sample code do not match.
For example for the specific electronic heat, Ce, Mareev et al. uses a_0 = 0.005 and the coefficients of higher order Te terms are set to 0 in the equation for Ce. However, the sample code uses a_0 = -0.00012899 and the other coefficients (a_1, a_2, etc.) are non zero values.
My understanding is that the coefficients in the fix ttm/mod model for specific electronic heat are inherent to silicon and would not change based on conditions which are independent of the electron temperature. For such parameters, are values found in literature or do they have to be calculated for the specific system I am trying to model? I would find it helpful to understand how the values for the sample code were attained as a starting point.
Thank you!