ENHANCE — Increase the matrix form used in sparse PSOLVE.

ENHANCE

When using PSOLVE with SPARSE, a fixed matrix form is used when solving for the density. ENHANCE means that some additional elements should be included in the determining this matrix form. This may be helpful for certain jobs that encounter convergence trouble using the default matrix form. It may slightly increase the memory and CPU usage as a consequence.

The default fixed form used in PSOLVE is combined forms of P, F, F*P, and P*F, where P is the current density
matrix and F is the Fock matrix. For PSOLVE=CGDMS or QNDMS, using ENHANCE adds elements based on the
matrix P*F*P. For PSOLVE=PDM, CEM, and SIGN, the extra elements are taken from
P_{0}*P_{0}, where P_{0} is the PDM initial guess density matrix.

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