If you can to help me to calculate and plot the total energy as a function of volume using the castep code implemented in the biovia materil studio software
Dear Mohamed,
There are several ways you could do this. The simplest methods are either:
1) Take your unit cell in Materials Studio, and build a set of similar unit cells whose lattice constants are increased by 1%, 2%, 3% etc. (and similarly for decreased ones). This could be automated fairly easily if you are happy writing scripts, and if you have Pipeline Pilot there might even be a protocol to do this already. The delta-project did something similar for the elemental materials, so you could look at their scripts:
https://molmod.ugent.be/deltacodesdft
Once you have your unit cells, you just run each one with CASTEP, note the volume and total energy, and plot in your favourite plotting package.
2) Take your unit cell and apply a hydrostatic pressure to it, then perform a variable-cell geometry optimisation. Note all the volumes and energies as the calculation progresses, and plot in your favourite plotting package.
Method 1 is probably the simplest in terms of understanding what you're doing and how it all works, and will give a uniform sampling of the compression (tension). However, method 2 will probably be quicker as it can re-use the density and Kohn-Sham wavefunctions from earlier steps.
For each method you could also get more information by noting the pressure for each energy-volume (E-V) point; the pressure tells you dE/dV so you get the gradient of the curve at that point, in addition to the value. The stress is computed automatically in Method 2, but if you do Method 1 you'll need to tell CASTEP specifically to compute it:
calculate_stress : true
in the .param file.
Hope that helps,
Phil Hasnip
(CASTEP developer)
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