Force constants calculated by Gulp 5.2 and gulp 6.2 are different

Hello, it is found that the force constants calculated by gulp 5.2 and gulp 6.2 are different. I wonder why this happens. Can anyone give some advice?

==> FORCE_CONSTANTS_2ND_gulp5.2 <==
4096
1 1
15.482761375177 -0.000000000000 -0.000000000000
-0.000000000000 15.482761375177 -0.000000000000
-0.000000000000 -0.000000000000 15.482761375177
1 2
0.000000000000 0.000000000000 0.000000000000
0.000000000000 0.000000000000 0.000000000000
0.000000000000 0.000000000000 0.000000000000
1 3

==> FORCE_CONSTANTS_2ND_gulp6.2 <==
4096
1 1
12.380062737285 -0.000000000000 -0.000000000000
-0.000000000000 12.380062737285 -0.000000000000
-0.000000000000 -0.000000000000 12.380062737285
1 2
0.000000000000 0.000000000000 0.000000000000
0.000000000000 0.000000000000 0.000000000000
0.000000000000 0.000000000000 0.000000000000
1 3

In order to investigate this it would be useful if you could post your input file please, otherwise it’s hard to know where the numbers come from and why they might be different.
Thanks,
Julian

Having seen your input file, you’re using bond order potentials (Tersoff-style potentials for example). There have been significant changes to the code from version 6.0 as to the form of these bond order potentials and default handling of parameters. Therefore you’d need to carefully check the form of the potential you want to achieve and how to input it so that it matches the behaviour for the particular version. To illustrate this, if you look in the libraries of potentials provided for Tersoff there are notes indicating that the latest library should only be used with version 6.0 onwards. I’d recommend you stick with the latest version and use this for your work. I’d also note that there may be issues with the file formats for shengbte (which you have in your input) and I’d recommend using GULP with Alamode which is known to be compatible and there are examples to show how to use the two codes together.

Are the force constants calculated using my current inputfile with gulp-5.2 correct?

That’s not a question I can answer since it depends on what formalism you intended to run with and the parameters were derived for. Hence you’ll need to check against reference data from the publication for the model whether what you’ve input is correct. I’d suggest sticking with the latest version of the code since the formalism implemented there is more general and flexible, rather than using an old version.