INSTRUCTIONS FOR DAY 1, EXERCISE 4
In this exercise, we will use PWSCF to obtain the equilibrium structure of some simple crystals
- Enter the directory ex4. Copy the silicon input file and pseudopotential from example 1
- Edit the input file to perform a variable-cell geometry optimisation by setting calculation='vc-relax'.
- Add the following IONS and CELL name lists (after ELECTRONS)
&ions upscale =100 / &cell Press = 0.0 /
- Press is the target pressure in KBar (1KBar = 0.1 GPa)
- Run the geometry optimisation
- Examine the output file - how does the lattice constant compare to experiment. Note that the forces on the ions are zero due to symmetry.
- Repeat the calculation at a higher pressure
- Run the geometry optimisation for As at zero pressure (As0.bfgs.in is provided)
- Repeat the calculation at 40GPa - what do you observe? Look at the output with Xcrysden. It may help to glance at Physical Review B 78, 174101 (2008) doi:10.1103/PhysRevB.78.174101