how to handle the problem about "Sub-Space-Matrix is not hermitian in DAV "

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ZHEGV is a LAPACK routine which computes all the eigenvalues, and optionally, the
eigenvectors of a complex generalized Hermitian definite eigenproblem.

If the problem occurs during relaxation of the ions, the most probable
reason for the error is that the system has relaxed to a pathologic
geometry. Please have a look at the ionic relaxation history.
To avoid too large steps from one ionic configuration to the next, decrease
POTIM (0.1 seems a reasonable value in most of these cases)
and/or try IBRION = 1