Dear All,
I want to simulate fs laser ablation on silicon. I want to look into the heat damages caused by laser ablation. My problem is that I don’t know how to include laser deposition by LAMMPS. Any advise is highly appreciated.
Regards,
Leyla
There are 2 two-temperature models in Lammps, one through fix ttm and one through fix atc that you could try.
Jeremy
My question is for example if I want to apply a 0.5 J/cm2 laser to my system, where should I include that intensity in the fix ttm.
You can also try something simpler: fix heat
which will add energy to the atoms in a region.
Steve
Dear Steve,
Thanks for your reply. I already applied "fix heat" to silicon and I can predict the temperature profile of atoms. But as I am working on fs laser ablation and in that case, effect of electrons should not be neglected, I am wondering how can I get the temperature profile of electronic system. In "fix-ttm" command it is possible to see the electronic effects but I don't know how should I apply the heat source in that command.
Regards,
Leyla
Paul can probably provide a more detailed answer.
Steve
"fix ttm" represents that hot electrons and acts as a heat reservoir that interacts with the atoms. Please carefully review the documentation page (http://lammps.sandia.gov/doc/fix_ttm.html) and the relevant literature, including the following:
(Duffy) D M Duffy and A M Rutherford, J. Phys.: Condens. Matter, 19, 016207-016218 (2007).
(Rutherford) A M Rutherford and D M Duffy, J. Phys.: Condens. Matter, 19, 496201-496210 (2007).
IOP PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER
J. Phys.: Condens. Matter 22 (2010) 225405 (8pp) doi:10.1088/0953-8984/22/22/225405
Electron-ion coupling effects on simulations of radiation damage in pyrochlore waste forms
Ahmed E Ismail, Jeffery A Greathouse, Paul S Crozier and Stephen M Foiles
(especially see Table 1)
C. L. Phillips and P. S. Crozier, J. Chem. Phys. 131, 074701, 2009.
Phillips, Magyar, and Crozier, J. Chem. Phys. 133, 144711, 2010.
There's no quick and easy way to get the input conditions and parameters for this kind of TTM simulation. You'll probably have to do some calculations, make some approximations, and recognize your eventual models' weaknesses.
You'll need to carefully consider that time window that you are trying to simulate and what the appropriate boundary and initial conditions should be. I assume you'll want to simulate from the moment the laser pulse ends. If so, compute the total energy deposited by the laser, and include that energy in your initial conditions, then simulate the dissipation of that energy. You'll have to figure out all of the specific details of your model and set the input conditions and parameters accordingly.
Paul
Thanks Paul,
I have already simulated the energy deposition and dissipation according to Beer-Lambert law with "fix-heat" command in LAMMPS in my system. But in order to have electrons in the system, I have to convert to "fix-ttm" and my question is, once I realize all the initial conditions and parameters, how do I pump heat to the system? In the "ttm" command I see the optical properties not the heat source parameter.
Regards,
Leyla
Fix TTM transfers energy between the atoms and a finite heat reservoir representing the electrons, whereas fix heat transfers energy between the atoms and an infinite heat reservoir at a constant rate. You'll have to decide which is the better model for your problem. Might even make sense to use both at the same time. Or, you may conclude that neither one is a good match and decide to create your own "fix".
Paul
Hello,
In my simulation as it is laser ablation , I should have periodic boundaries in X and Y direction not in Z direction. However in "fix-ttm" the boundaries are in X,Y and Z direction. how can use this command and not have periodic boundaries in Z direction.
Regards,
Leyla
You'd have to modify the source code to make fix TTM non-periodic in Z.
Paul