I am a PhD student new to GULP, and I am trying to calculate the elastic tensor of various crystalline materials at elevated temperatures. I have successfully used the ZSISA model in GULP, but given the underapproximation of the effects of thermal expansion (as described in the manual), I would like to attempt this using MD in GULP to get more physically accurate results. However, as I am new, I don’t know how to set up an input file for MD, beyond what is in the example files, to calculate these data. Could anyone offer any guidance on how I might approach this, if it is possible?
For temperature effects and thermal expansion it’s important to consider whether you are interested in things above or below the Debye temperature. Below this MD will give inaccurate results since it doesn’t quantise vibration or include zero point energy, whereas at high temperatures anharmonicity is important and so the quasi harmonic approximation breaks down.
As for how to run MD, the short answer is that your supervisor should find a co-supervisor who is an expert in MD to provide the training and to ensure that everything is performed correctly.