Isothermal optimization

GULP
1

Dear GULP developers,

I am sorry to bother you, but I have a question to ask you. I have been using GULP for isothermal optimization, and I have encountered a perplexing situation. After multiple attempts, I found that no matter what temperature conditions I set for the calculations, the lattice constant did not change in the end. That is to say, the lattice constants remained the same under different temperatures. I have tried switching to different potential functions and models, but the issue persists.

I am very curious to know the specific reason for this problem. Why is it that the lattice constant does not change under different temperatures during isothermal optimization? Is it possible that I made an error in writing the input file, leading to the failure of achieving isothermal optimization? If so, how should I correctly write the input file for isothermal optimization?

Thank you very much for your help and patient guidance. I look forward to your valuable advice and suggestions.

Warmest regards,
LiMa
cont-opt.gin (7.8 KB)
slurm-4964921.out (36.8 KB)
bush.lib (1.7 KB)
slurm-8135858.out (36.9 KB)

2

Dear LiMa,
This is only perplexing if you don’t read the manual or study the theory before you run the calculation. :slight_smile:
You’ve run an athermal optimisation of the internal energy & so this doesn’t depend on the temperature. Hence nothing happens if you change the temperature! If you want temperature effects then you need free energy minimisation, but make sure you’ve read all about the theory and issues before you start otherwise you’ll have a difficult time since there are plenty of things that can go wrong with such calculations if you don’t know what you’re doing.
Regards,
Julian