[molpro-user] [SOLVED] Re: 0.1 h differences in HF energy with and without symmetry

[Benj FitzPatrick]

Dr. Werner,
Thanks for the suggestion of the shift levels.  Also, you are correct about the
occupation, I had specified the incorrect irrep.  Sorry for the trouble.
Thanks,
Benj

---- Original message ----
>Date: Tue, 27 Oct 2009 12:09:01 +0100
>From: Hans-Joachim Werner <werner at theochem.uni-stuttgart.de>  
>Subject: Re: [molpro-user] 0.1 h differences in HF energy with and without
symmetry  
>To: Benj FitzPatrick <benjfitz at uchicago.edu>
>Cc: molpro-user at molpro.net
>
>Either you found a wrong state when using symmetry (wrong occupations),
>or the calculation did not converge. Using Version 2009.1 (patchlevel  
>21)
>I found that  shift,-0.5,-0.5 helps to reach convergence, and then one  
>gets the
>same energy (-191.29326461) with and without symmetry. In the  
>calculation with
>symmetry it automatically finds the correct ground state (symmetry 2).  
>In cases
>where the Aufbau principle does not work correctly it may be helpful to
>specify the wavefunction symmetry and the occuptions; in the present
>case the input should then read
>
>{hf;occ,13,3;closed,13,2;wf,31,2,1;shift,-0.5,-0.5}
>
>but - as already mentioned,
>
>{hf;shift,-0.5,-0.5}
>
>also works in the present case. Note that the latter input would not  
>work with
>older Molpro versions, which always assumed wavefunction symmetry 1
>if no wf card was given.
>
>Joachim Werner
>
>
>Am 26.10.2009 um 19:22 schrieb Benj FitzPatrick:
>
>> Hello,
>> I found convergence issues with the below molecule when using large  
>> basis sets
>> (> aug-cc-pvtz), and in trying to understand that I found that I get  
>> very
>> different HF energies (> 0.1 h) when symmetry is used (Cs) versus  
>> when nosym is
>> specified.  More specifically, nosym gives lower energies by more  
>> than 0.1h.  I
>> haven't noticed this problem with any of the 20 other intermediates  
>> in this
>> system.  I performed similar calculations using g03's ROHF and it  
>> gives the same
>> energy as I get without symmetry in molpro.  I also used MCSCF to  
>> look for
>> low-lying excited states, and there aren't any.  Is this just a  
>> problem case for
>> molpro's UHF/ROHF or is something more insidious going on?
>> Thanks,
>> Benj FitzPatrick
>> University of Chicago
>>
>> ***,rohf sp of int7 from c3h5o-int7-cis-cis-eq_opt-ccsd-avdz-vtight- 
>> a.log***
>>   memory,100,M
>> gthresh,oneint=1.d-12,twoint=1.d-12,zero=1.d-12
>>
>> hc2=1.09590208
>> hc3=1.09184279
>> hch3=116.45662125
>> cc4=1.39830438
>> cch4=122.79284718
>> dih4=180.
>> hc5=1.09513808
>> hcc5=118.60649215
>> dih5=0.
>> cc6=1.39907689
>> ccc6=126.2456274
>> dih6=180.
>> oc7=1.3692314
>> occ7=125.04755482
>> dih7=0.
>> ho8=2.04723683
>> hoc8=29.55891751
>> dih8=180.
>> ho9=0.9660072
>> hoc9=109.16122263
>> dih9=0.
>>
>> geometry={
>>    ang;
>>   nosym;
>> C;
>> H,1,hc2;
>> H,1,hc3,2,hch3;
>> C,1,cc4,2,cch4,3,dih4;
>> H,4,hc5,1,hcc5,3,dih5;
>> C,4,cc6,1,ccc6,3,dih6;
>> O,6,oc7,4,occ7,1,dih7;
>> H,7,ho8,6,hoc8,4,dih8;
>> H,7,ho9,6,hoc9,4,dih9;
>> }
>>
>>   basis=6-31G*;
>> {hf;
>>   wf,31,1,1}
>> _______________________________________________
>> Molpro-user mailing list
>> Molpro-user at molpro.net
>> http://www.molpro.net/mailman/listinfo/molpro-user
>