hello,
i want to find diffusivity in solid electrolyte by creating vacancy , i followed following steps if anyone can suggest me if any error or better suggestion please. performed all calculations in Quantum espresso
1. created 2x2x2 structure
2. preformed vc - relax ( optimization in atom position and shape/volume)
3. created vacancy by removing 1 Li atom
4. again performed vc relax (optimization in atom position and shape/volume)/ or do we need to performed just relaxation ( atom position) here ?
5. NVT MD simulation at various temp to find MSD and then diffusivity and ionic conductivity.
i find in some research first to performed NPT equilibration then NVT , may you please help me to understand this procedure?
Hey Rahul Sharma
Your workflow looks good, but I do have a couple of suggestions to, perhaps, improve it. After creating Li vacancy, do a regular relaxation (atomic positions only). Vacancy shouldn't drastically change the overall cell shape or volume. It is expect to be local distortions only. As far as I am aware of, NPT equilibration is performed to relax the stress and adjust volume because creating a vacancy can disturb the local pressure. NVT, on the other hand, deals with constant volume and temp.
It’s something like, Li vacancy causes local changes, and NPT makes the necessary adjustments. Then, switch to NVT to gather meaningful diffusion data.
I hope that helps,
Rgds
Gabriel Vinicius thank you for suggestion and information, as you mentioned I am planning to perform NPT equilibration and then NVT MD simulation On relaxed (atomic position only) structre.
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