problems about Elastic Constants under certian pressure

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1

Dear LAMMPS developers and users,

I want to obatian the elastic constants of cubic silicon carbide under certian pressure. Then I used the ELASTIC example provided in the LAMMPS distribution and changed some commands in the input scripts for adapting to my purpose. Especially, the command “fix 3 all box/relax aniso 0.0” was varied to “fix 3 all box/relax aniso ${press}”, where the variable press is the certian pressure. After tested a couple of different pressure values, I found that the elastic constants were nearly unchanged. However, as shown in some papers the elastic constants change with the pressure of system. Therefore, I consider I must miss some essential seetings. Would someone (especially Aidan) familiar with the elastic constants calculation give me some advice. Any suggestion would be of great help.

Thans & Regards

Landauf

2

Well, if the elastic constants are nearly unchanged, it could be that the specified pressure is too small to have an effect. Try making it larger. You can also achieve a similar goal by simply changing the initial lattice constant, removing the fix box/relax command. You will get a non-zero initial pressure that is recorded in the log file.

3

Dear Aidan, thank you so much.

With your advice I checkd my scripts and found that I had made a mistake that the units used in the simulation was neglected. I would try it again.

Best regards.

Landauf

2016-03-23 08:14:35，“Aidan Thompson” <aidan.thompson@…24…> ：