As general information, Beta is a scaling of the predicted step. Earlier versions of the mixer used an algorithm based upon improvements for this, in the more recent version (improved in the next one, 10.5) it is estimated from the previous history. A value of 0.05 means that the mixer thinks that the predicted step is very inaccurate.
The specific case (deleted for size limits on emails) was taking very small steps (e.g. "Newton 1.00 0.0016") which are ~1E-3 of the a Pratt step, which is already small as the calculation is closed to converged (:DIS < 1D-3). With a GREED of 0.002 this means that the unpredicted step is also small, and both are ~1D-6 (:DIRT : |MSR1|= 2.768E-06). Very small steps are susceptible to numerical noise and ill-conditioning. All mixers employ Simplex differentiation which is a form of numerical differentiation so susceptible to such problems. I have not analyzed in detail myself the conditioning/noise of SOC in Wien2k. Peter's recommendations are almost certainly ones which improve the conditioning. -- Professor Laurence Marks Department of Materials Science and Engineering Northwestern University www.numis.northwestern.edu Corrosion in 4D: www.numis.northwestern.edu/MURI Co-Editor, Acta Cryst A "Research is to see what everybody else has seen, and to think what nobody else has thought" Albert Szent-Gyorgi
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