CCL: Question on NWChem run (UHF, singlet)



 Sent to CCL by: Wirawan Purwanto [wirawan0 a yahoo.com]
 Hi,
 I am a new member of this list, and I appreciate the opportunity to
 join CCL.
 I have a question concerning running NWChem for UHF calculations for
 singlet states. Let's take, for example, a water molecule (H2O) or a
 singlet dimer (such as Li2, P2, etc.).
 Naive setting
 scf
   uhf; singlet;
 end
 task scf energy
 would simply give the RHF result, so let's not discuss that. I got some
 suggestion to use
 scf
   uhf; singlet
   vectors swap alpha 4 5 swap beta 5 6
 end
 for a water molecule (STO-6G basis), but this does not get to the
 lowest UHF energy. I have been trying swapping different states, it
 would not yield any positive progress.
 Prior to this, I used GAMESS, and I could run the singlet/UHF run
 easily (I'm not for or against one package or the other, though). What
 I did with GAMESS was to use the RHF final configurations as the
 initial "alpha" states, and random configurations as the initial
 "beta"
 states -- usually I'm lucky this way, and got the UHF total energy
 lower than the RHF total energy.
 Now, with NWChem, I could not find a way to fully "customize" the
 initial configuration (i.e. specify the vector elements directly). The
 only way I know is to use *.movecs file generated priorly. I don't have
 time or energy to create my own *.movecs, though.
 Does anyone has any suggestion? Or if you need more detail to answer my
 question, I will gladly provide it.
 Thanks,
 Wirawan
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