Subject: Re: QUESTION STABILITY_KEYWORD?

From: Wai-To Chan <chan:at:curl.gkcl.yorku.ca>
Date: Thu, 22 Jul 2004 04:51:58 -0400 (EDT)

From: Paul Momoh 

<<<<<<<<<<<<<<<<<,,
Good morning,
I initially performed a stability job (STABLE) on a DFT (B3LYP) job. I
got the message RHF-> UHF instability. I then performed another
stabilty test (using Stable=repopt). The instability was subsequently
corrected (I got a lower abs energy). Where/how can I get the
corrected coordinates and/or multiplicity and/or method used for the
corrected structure?

	  By 'corrected' structure you probably mean the structure 
obtained from geometry optimization with the stable wavefunction. 

		 If you have the reoptimized wavefunction saved in your checkpoint
file you can easily start a geometry optimization job with 
unrestricted B3LYP this way

# ub3lyp/(basis set) guess=read opt 

   Provided that the ub3lyp solution does not converge back to 
rb3lyp during the course of geometry optimization your job
may pick up a different structure. In some cases if the structure
has spatial symmetry it may be necessary to specify scf=nosymm
to prevent the collapse of the unrestricted solution back to 
the unstable restricted solution. 

  Whether the obtained structure is correct or not may or may 
not be contingent on the stability of the wavefunction. 

Wai-To Chan