node counting threshold parameter

[cffischer]

Wave functions such as c_1 | 1s(2) 1S > + c_2 |1s 2s 1S> have energy expressions with off-diagonal I(a,b) integrals for which the stationary solution for 1s has an additional node. The node counting procedure will dismiss nodes associated with small amplitudes when varying both orbitals. In this case, the 1s orbital is still classified as nodeless. This amplitude is set in the rmcdhf90/getscd.f90 by the parameter THRESH = 0.05D0. While testing this case, CYC and CFF found that the iterations converged when the THRESH parameter was increased and we recommend the use of THRESH = 0.10D0 . Systematic tests have not yet been performed but it is possible that, with this change, the LBL process may be delayed, so that more orbitals can be varied simultaneously and only correlation orbitals with small energy corrections are included by the LBL processs.