Subject: convergence failure

From: [email-masked] (Dawn Friedman)
Date: Thu, 14 Jan 93 13:05:52 -0500

I'm using G88 to do UHF calculations with a large basis set on some alkali
oxides.  I'm feeling out a reaction path using single-point calculations
(optimizations to come later.)  Some of these single points give me a 
convergence failure in SCF, although an energy is reported first.
  
1)  Does this energy have any meaning?

2)  Why should one geometry converge, while another, differing only by the
C_inf_v symmetry being broken (180 -> 179.9 degrees) does not?  The energies
are identical.  Sometimes the nonlinear version will converge where the linear
did not.
  
3)  Can I work around this problem and still have useful results?  Is there
some method a bit less sweeping than the SLEAZY keyword for getting SCF
convergence?  Unfortunately, I can't afford to do SCF=qc -- they take too long
and often don't converge anyway.
  
  --Dawn