File structure of the *.frc file

GULP
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1

Hello,

I compute the force constants through the phonon calculations, but a very complex file is generated in which I can not extract the force constant of relevant bond.

Could you please help me to understand the file structure?

Best regards

Emre

2

Hi Emre,

You would need to be specific as to exactly which file you’re referring to in order to specify the format, though they are rarely designed to be human readable, but instead are usually for post-processing with another code. In general, the force constants output are the 2nd derivatives of the energy in Cartesian space and so there is no force constant for a specific bond. This is usually an input to the code when you specify a harmonic or Morse potential etc.

Regards,

Julian

3

Thank you Prof.

My another question is related to the Alamode. Using Alamode, I could get the 2nd force constants between each pair of atoms. However, there is no additional file (fcs) appears having interatomic force constants. How can I generate this under GULP? When I add a line such as output fcs (or xml) name_of_calculation, there is nothing appears.

Input and output are enclosed.

Best regards

Emre

AAAA.got (242.5 KB)

AAAA.gin (27.1 KB)

4

fcs and xml are file formats for Alamode and not GULP. Hence asking GULP to output them won’t make any sense. You can check the help text for available file formats under the “output” option (which does include ones that output the force constant matrix or second derivatives). However, if you run a calculation of thermal conductivity using GULP linked to Alamode then the fcs and xml files are written by Alamode during the process.

5

Yes Dear Prof.

I am trying to obtain the force constants between atoms through fcs files, however I can not generate them.

Could you please review my input file and point out my mistake?

Best regards

Emre

6

Just run example67 that comes with GULP and you’ll get a fcs file. If this fails it means you haven’t installed Alamode with the right version or as per the instructions in the README. Once this example works, all you have to do is change the details to be your system.