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Delaying switching to NR method

Slawomir Janicki
slawomir.janicki@comcast.net


Hi,
How can I delay switching from GDIIS to NR method in geometry optimization?

When NR kicks in a large step causes SCF convergence to fail, presumably because of a bad guess. I tried to decrease DXMAX to 0.001, but there seems to be no effect on when NR starts.

Is there a better way to delay or prevent switching to NR? Alternatively, is there a way to reduce the NR step size?

Below is an example of the step when NR starts:

          MAXIMUM GRADIENT =  0.0462724    RMS GRADIENT = 0.0142135
          FORCE CONSTANT MATRIX NOT UPDATED --- TAKING FIRST STEP
          MIN SEARCH, CORRECT HESSIAN, TRYING PURE NR STEP
               NR STEP HAS LENGTH         =  92.651197
          TRIM/QA LAMBDA FOR NON-TS MODES = -84.40598785
          TRIM/QA STEP HAS LENGTH         =   0.001000
          RADIUS OF STEP TAKEN=   0.00100  CURRENT TRUST RADIUS=   0.00100
          TRANSFORMING DISPLACEMENT FROM INTERNALS TO CARTESIANS
          THE ROOT MEAN SQUARE ERROR IN ITERATION   1 IS   0.00000001
          THE ROOT MEAN SQUARE ERROR IN ITERATION   2 IS   0.00000000
          MAX PRIMITIVE INTERNAL COORDINATE DEVIATION IS   0.00000000
          INTERNAL COORDINATES SELF-INCONSISTENCY     IS   0.00000303

Slawomir


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