[fix ttm/mod]surface movement of electron temperature field


i m trying to use ‘fix ttm/mod’ to study the laser melting of Au foil and i met some problem.

in the ‘fix ttm/mod’, we can set the surface movement parameter as ‘1’ to enable the expansion of electron temperature field. as follows is the description:

The current fix ttm/mod implementation allows TTM simulations with a vacuum. The vacuum region is defined as the grid cells with zero electronic temperature. The numerical scheme does not allow energy exchange with such cells. Since the material can expand to previously unoccupied region in some simulations, the vacuum border can be allowed to move. It is controlled by the surface_movement parameter in the init_file. If it is set to 1, then “vacuum” cells can be changed to “electron-filled” cells with the temperature T_e_min if atoms move into them (currently only implemented for the case of 1-dimensional motion of flat surface normal to the X axis). The initial borders of vacuum can be set in the init_file via lsurface and rsurface parameters.

in this case, we should set the ‘T_e_min’ value in order to initialize the new cell. And my problem is, what is proper value for a initial cell in the case of ultrafast laser melting? if i set 300K as the minimum of electron temperature, the electron-phonon energy transfer would be too weak.

and i chose the T_e in the boundary for initiation by modifying the fix_ttm_mod.cpp file. the part is shown as follows:

original: T_electron[ixnode][iynode][iznode] = electron_temperature_min;
modified : T_electron[ixnode][iynode][iznode] = T_electron[t_surface_l][iynode][iznode];

After my modifying, the new activated cell has the enough high electron temperature, however, the energy transfer between electron and lattice is dismissed, which leads to the unchanged electron temperature in these new cells. Is my modifying correct?

so, how to make sure the new activated cell has the proper electron temperature both with effective energy transfer between two system?

I suggest you email the authors of fix ttm/mod, listed in the src/USER-MISC/README file.