Cu lattice constant

As a second example of an intersting physical property to calculate we looked at the lattice constant of bulk Cu.

Our tasks here:

• Calculate the total energy of the system with different lattice constants. The lattice constant was most easily modified by changing the scaling factor in the input file.

• Some important notes:

• In each of the calculations the setup depended files (broyd, broyd.7, fl7para, pottot, potcoul, stars, wkf2) must be removed.

• The density (cdn1-file) must either removed as well (the start with generating a new one for each lattice constant) or might be tried to reused.
• To improve accuracy, we should increase the planewave cutoff for the basis functions to ~4.0 a.u.
• Only small variations of the lattice constant (a few percent) are expected to give reasonable results.

• For reducing the lattice constant we might also have to reduce the MT-radius, but be carefull, the total energies can not be compared for calculations with different MT-radii. So you have to use the same MT-radius for all scaling factors you want to use.

• One should get pairs of energy versus scaling-factor like this: