Subject: convergence

From: Jolanta Grembecka <[email-masked]>
Date: Mon, 26 Apr 1999 12:13:19 +0200

Dear CCLers,

I would like to perform an optimization of inhibitor in the active site
of the enzyme, using ONIOM in Gaussian98. Some of the enzyme active site
fragments are frozen, while others as well as inhibitor are free to
move. However, there is a problem with convergence in third step of the
optimization. This is a fragment from the output file:
------------
GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
 Berny optimization.
 Use GDIIS/GDPIS optimizer.
 Internal  Forces:  Max     0.122271245 RMS     0.022900677
 Search for a local minimum.
 Step number   3 out of a maximum of 390
 All quantities printed in internal units (Hartrees-Bohrs-Radians)
 Swaping is turned off.
   2   1 -0.2994080E-01  0.1587312      0.1886258
 Update second derivatives using information from points  2  3
 Trust test= 3.55D+00 RLast= 2.67D+00 DXMaxT set to 6.00D-01
 RFO step:  Lambda= 3.07895529D-02.
 Cosine:  0.361 <  0.866
 Cut down GDIIS temporarily because of the cosine check. E 7
 Maximum step size (   0.600) exceeded in Quadratic search.
    -- Step size scaled by   0.923
 SLEqS1 Cycle:  1951 Max:0.182663E-01 RMS:0.288751E-02 Conv:0.830925E-06
 SLEqS1 Cycle:  1951 Max:0.547130     RMS:0.725821E-01 Conv:0.830925E-06
 Iteration  1 RMS(Cart)=  0.07678248 RMS(Int)=  0.04090075
 SLEqS1 Cycle:  1951 Max:0.309281     RMS:0.644244E-01 Conv:0.348998E-06
 SLEqS1 Cycle:  1951 Max:0.103404     RMS:0.178235E-01 Conv:0.348998E-06
 Iteration  2 RMS(Cart)=  0.03887554 RMS(Int)=  0.01798566
 SLEqS1 Cycle:  1951 Max:0.210165     RMS:0.233334E-01 Conv:0.229509E-06
 SLEqS1 Cycle:  1951 Max:0.573045     RMS:0.728841E-01 Conv:0.229509E-06
.
.
.
.
.
(the lattest iteration) 
Iteration 99 RMS(Cart)=  0.04352782 RMS(Int)=  3.41598486
 SLEqS1 Cycle:  1951 Max:0.400389E-02 RMS:0.688668E-03 Conv:0.200000E-06
 SLEqS1 Cycle:  1951 Max:0.145725E-01 RMS:0.184286E-02 Conv:0.200000E-06
 Iteration100 RMS(Cart)=  0.02664367 RMS(Int)=  3.39771394
 Curvilinear step not converged.
 Error imposing constraints
 Error termination via Lnk1e in /d2/PROGRAMY/g98/l103.exe.
--------------------

How to resolve this problem?

Jola Grembecka
Institute of Organic Chemistry, Biochemistry and Biotechnology
Wroclaw University of Technology