Orbital $DEL Optimizations

Orbital $DEL Optimizations

Postby cd1435 » Thu Mar 27, 2014 9:06 pm

Hello,
I am having particular trouble getting an optimized structure after deleting orbitals (using $DEL) using B3LYP/6-311G** calculations (thru G09 RevD) on monocyclic structures. The calculation seems to always fail with this error:

Code: Select all
 WARNING| EIGENVALUE 48 TOO LARGE. REPLACED BY    25.000000
 WARNING| EIGENVALUE 47 TOO LARGE. REPLACED BY    25.000000
 WARNING| EIGENVALUE 46 TOO LARGE. REPLACED BY    25.000000
 WARNING| EIGENVALUE 45 TOO LARGE. REPLACED BY    25.000000
 WARNING| EIGENVALUE 44 TOO LARGE. REPLACED BY    25.000000
 HESSIAN DOES NOT HAVE THE DESIRED LOCAL STRUCTURE
 TAKING SIMPLE RFO STEP
 SEARCHING FOR LAMDA THAT MINIMIZES ALONG ALL MODES


 *****************************************
 *** UNABLE TO DETERMINE LAMDA IN FmD114 **
 *****************************************


and for reference, eigenvaleus 44-48 are listed in my output as:
Code: Select all
 
   44        45       46        47        48
28.49815  67.56663 72.29492  78.67816  79.09973


I have tried an even smaller basis set to see if that could cause this, but the same error persists.
What is going wrong here? How do I fix this error??
cd1435
 
Posts: 5
Joined: Thu Mar 27, 2014 8:48 pm

Re: Orbital $DEL Optimizations

Postby ericg » Sun Mar 30, 2014 12:57 pm

I suspect that the Natural Lewis Structure (the pattern of bonds and lone pairs found by NBO) is changing during the course of the optimization, yielding localized energies associated with different NLS energy surfaces and thereby confusing the optimization algorithm.

Use $CHOOSE to avoid this problem. See that sample G09 input file near the bottom of the deletions tutorial on the NBO6 website (http://nbo6.chem.wisc.edu/tut_del.htm). $CHOOSE directs NBO to find a specific NLS.

Eric
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Re: Orbital $DEL Optimizations

Postby cd1435 » Thu Apr 03, 2014 2:56 pm

I have tried what you suggested, using $CHOOSE, and I receive the same error as before.

Although, I have tried the sample calculation in the tutorial and it completes with no problem.

Does the number of variables to optimize effect this?
cd1435
 
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Re: Orbital $DEL Optimizations

Postby ericg » Sun Apr 06, 2014 12:47 pm

Would you mind posting your input file here so that I can try it myself, or forward it to me at glendening@indstate.edu.

Eric
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Re: Orbital $DEL Optimizations

Postby cd1435 » Tue Apr 15, 2014 8:20 am

Do you have any updates on this?

Were you able to figure out the issue?
cd1435
 
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