View source for Energy-Volume Curves

[[ICME_2013_HW1| < Homework 1 (2013) Overview]] <br>
[[ICME_2015_HW1| < Homework 1 (2015) Overview]]

=Objectives=
* Plot an energy vs. volume curve for aluminum in a FCC crystal structure.
* Perform a K-Point convergence study
** Use default energy cutoff provided in the pseudo-potential file.
** Plot equilibrium energy per atoms vs. K-Point grid
** Plot CPU time vs. K-Point grid
** Choose the K-Point grid that corresponds to the energy convergence of 1meV with minimum time
*Perform a convergence study on the energy cutoff value
** Use converged K-Point grid calculated previously
** Plot energy vs. volume curves for 70% and 130% of the maximum energy value.
* Using converged K-Point grid and energy cutoff value plot converged energy vs. volume curves.
* Derive an equilibrium lattice constant and a bulk modulus from the final EV curve

=Instructions=

==VASP Guide==
* Refer to this [[VASP in batch mode| walk-through]] for running VASP in parrallel.

==Executable and Potential Files==
* Navigate to <pre> /cavs/general/ICME_2013/Homework_1/VASP</pre>
** This directory contains the VASP executable and POTCAR files needed for this assignment.
** Make sure to download the correct POTCAR file specific to each group.

==VASP Input Files==
* Copy the INCAR and KPOINTS inputs from [[VASP Inputs for ICME 2013|here]] to the VASP directory.
* This [[FCC Runscript|BASH script]] will generate a collection of POSCAR files.
** Copy it and store it in the VASP working directory.
* This [[Evfit]] subroutine is called by the BASH script to fit the VASP output energy to various equations of state.
** Copy and compile Evfit to the VASP working directory.

==Modify the Portable Batch System Script==
* Modify the PBS script from the [[VASP in batch mode| VASP walk-through]] by removing this line: <pre> mpirun -np 16 NAME_OF_EXECUTABLE</pre> and replacing it with this one: <pre> ./NAME_OF_BASH_SCRIPT </pre>
* Where "NAME_OF_BASH_SCRIPT" needs to be replaced by the name of the [[FCC Runscript|BASH script]].

=Convergence Studies=

* The second objective requires investigation of the the change in results due to a variation of parameters in the DFT calculations.
* <b>Note:</b> The FCC runscript is a series of VASP executions over a range of lattice parameters. These convergence studies enclose that process within a secondary loop over a range of new values. In other words the whole calculation is now a nested loop and consequently will take quite a bit more time to execute.
==K-Point Convergence==
* Copy this additional [[K-Point Variation|BASH script]] into a direcotry with the [[VASP Inputs for ICME 2013|VASP inputs]], the [[FCC Runscript|FCC runscript]], and the PBS script.
* Edit the PBS script to call this new K-Point variance script
* Submit the PBS script as before

==Energy Cutoff Convergence==
* Use this [[Energy Cutoff Convergence| BASH script]] to vary the energy cutoff value. 
*Edit the PBS script to call this ENCUT code.
*Vary the global break condition for the electronic SC-loop (EDIFF) and plot E-V curves

=Output=
The FCC run script will create a few additional output files on top of the ones that [[Code: VASP|VASP]] already makes.
* EvsA: A Text file containing an energy vs. lattice parameter curve in column form.
* EvsV: A text file containing an energy vs. lattice cell volume curve in column form.
* SUMMARY: A text file containing results for equilibrium lattice constant, bulk modulus, and energy per atom.

=License=
By using the codes provided here you accept the the [[CodeRepository:License Agreement|Mississippi State University's license agreement]]. Please read the agreement carefully before usage.

[[Category: Aluminum]]
[[Category: ICME Class]]
[[Category: VASP]]