44.2 Standard Problems

Problem:

The VSCF results are completely unreasonable and the STATUS printed in the output of the VSCF program differs from 0.0 for one or several modes.

Solution:

If the STATUS differs from zero, some eigenvalues corresponding to the modals are negative, which of course should not be the case. The first number of the STATUS refers to the maximum number of negative eigenvalues within the VSCF cycles, while the second number provides the number of negative eigenvalues in the last iteration. When negative eigenvalues occur the effective potential will not be updated. This enforces convergence but on cost of the accuracy. The only solution to this is to compute more accurate potentials, i.e. switch of the MULTI approximation or use larger grids etc.