Varying laser heat source intensity by location fix ttm/mod

I am working to model a laser incident on the surface of a sphere for melting/ ablation of core-shell nanoparticles. The init_file for ttm/mod allows you to specify the thermal properties of the laser heat source, duration, penetration, etc, but these parameters appear to be one dimensional. Due to the geometry of the surface, the laser flux will not be the same throughout the particle. I can specify initial temperatures on the grid in the ttm-input file varying by location (I create this file via matlab code), but for the heat source it is one-dimensional. Is there a way to have the intensity vary by radius, or have multiple layers of different intensity? Please let me know if you need more info. Thanks again in advance for all of the help,
-Mike

Any change in functionality will require changes to the source code.

a_0, energy/(temperature*electron) units
-0.00012899
a_1, energy/(temperature^2*electron) units
-0.0000000293276
a_2, energy/(temperature^3*electron) units
-0.0000229991
a_3, energy/(temperature^4*electron) units
-0.000000927036
a_4, energy/(temperature^5*electron) units
-0.0000011747
C_0, energy/(temperature*electron) units
1065
A, 1/temperature units
D_e, length^2/time units

Hi, I am confused about these parameters in ttm/mod. How these parameters should be set according to the model? Thanks in advance for all of the help.

Only you can know since they correspond to the properties of the (electronic) system you are simulating with fix ttm/mod.

Yes they are curve fitting parameters. So you need to look at the electron specific heat curve for the material you are modeling, and then you can use a curve fitting tool to find the values you need



I read the description of the document parameters and looked for the corresponding parameters in the article, but I still didn’t understand how to match the document parameters with the parameters in the article model. If you understand, please let me know, I would appreciate it!

Thank you for reply. But I can’t understand the content about “get the electron specific heat curve for the material you are modeling”. I would appreciate it if you could explain it more clearly.

There are obvious correlations between the quoted table and the parameters required for the LAMMPS input. If you expect that those will be a 1:1 match, you have been very lucky so far. Some amount of converting and reconstructing is usually required. For example, the “Thermal conductivity of lattice” entry obviously contains the various expansion coefficients, but you may have to reconstruct the settings required for LAMMPS through some reverse engineering. E.g. you can assume that the exponential term is either 1 (i.e. A = 0) or included in the a_0, a_1, a_2, a_3, and a_4 coefficients. By comparing units and checking with the detailed description in the paper, you should be able to get what needs to be included in the LAMMPS input.