I want to get a optimized orthorhombic structure using quantum espresso by the energy volume curve. Firstly I have some previously reported value of a, b ,c. I have already made a structure using VESTA. When I incorporate this data into espresso and run a scf calculation, it is giving me a high pressure and not the minimum energy. I have already written a script for calculating energy with changing a, another two for changing b/a and c/a . But in all the case, there is a difference between the lowest pressure and lowest energy in the energy vs volume curve. Can any one suggest me any way out to solve this problem?
Thank you in advance
Dear Pratic,
As you know espresso has "vc-relax" option, which optimize both cell parameters and atomic positions
Using &cell namelist introduce your structural consraints
Bests
Hi,
Try vc-relax calculation. It will give the optimized structure. Look at the below link, it may help you....
http://media.quantum-espresso.org/santa_barbara_2009_07/slides-exercices/Tutorial_stress.pdf
Dear Practical,
As suggested do the vc-relax calculation, it will give you the optimized lattice parameter and structure. Also. one more thing while doing vc-relax don't forget to add the cell and ions columns to the input file.
Thank you all. But espresso is doing a scf after vc-relax calculation. In this scf run, some pressure is coming, whereas pressure seems to zero in the end of vc-relax. Can any one explain me why this inconsistency comes?
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