Single zeta polarized and Double Zeta polarised

[abhishek77492652]

Hello sir,
I have calculated the chemical potential for silicon crystal (alpha silicon) using both the DZP ansd SZP basis set and get the value as -4.081992 eV and -4.265549 eV  respectively. Please tell me which one is more accurate .
Also mention how to select basis set  (like DZP, SZP,...) in different situation .

THANKS in advance

[Petr Khomyakov]

You may look at the total energy, not the chemical potential. Lower energy usually means more accurate basis set, because the total energy is a variational  quantity.

However, other physical quantities may not converge with respect to the LCAO-based basis set monotonously, so in that regard it is hard to say whether your electronic structure is already converged with respect the basis. You may want to use even more accurate basis set such as SG15-based one to have a better idea on this.

Another option is to use our plane-wave calculator in ATK-2017.2. Then you may systematically check for convergence of physical quantities with respect to the plane-wave bases basis set, by varying a single parameter, which is the kinetic energy cut-off.

[Jess Wellendorff]

In addition, the calculated chemical potential is not very meaningful in itself; you need to compare it to some other energy-quantity computed using the same pseudopotentials+basis set in order to use it.