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Re^4: Geometry optimization problem with MCSCF with ECP in C3 symmetry.

Alex Nest
comconadin@gmail.com


On Sat Aug 13 '16 4:21pm, Pedro Silva wrote
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>>>By the way, I understand that you do not recommend "symmetry" and you do not recommend "ROHF". But WHAT do you recommend?

>I recommend C1 point group (to allow unsymetrical occupation of orbitals in "symmetry-identical atoms", UHF (to allow unpaired alpha and unpaired beta electrons to reside in widely disparate orbitals) and "manual" construction of initial guesses using the method of Szilagyi, R. K. and Winslow, M. A. (2006) J. Comput. Chem., 27: 1385–1397 .

>You will still need a large amount of work and (especially) luck, though :-(

Do you mean that automatic SCF procudure performed by GAMESS do not result to the correct electronic structure?

As I understand (please correct me if I get wrong) if I have spin populations (alpha minus beta) like the following (for MULT=2):
    ATOMIC SPIN POPULATION (ALPHA MINUS BETA)
      ATOM         MULL.POP.                    LOW.POP.
   1 C            -0.009151                    -0.003594
   2 C            -0.009151                    -0.003595
   3 C            -0.009151                    -0.003595
   4 S             0.104176                     0.093758
   5 S             0.104176                     0.091590
   6 S             0.104176                     0.091881
   7 H             0.002742                     0.001566
   8 H             0.002742                     0.001568
   9 H             0.002742                     0.001573
  10 H            -0.003580                    -0.002788
  11 H            -0.003580                    -0.002778
  12 H            -0.003580                    -0.002779
  13 H             0.002742                     0.001566
  14 H             0.002742                     0.001572
  15 H             0.002742                     0.001567
  16 S            -0.446735                    -0.380294
  17 S            -0.446735                    -0.378648
  18 S            -0.446735                    -0.380551
  19 S            -0.675558                    -0.628123
  20 FE            0.908325                     0.833016
  21 FE            0.908325                     0.833580
  22 FE            0.908325                     0.833509
it is incorrect because I should have ~ -4 at one Fe and ~ +4 at the another one or something like this.

Or for MULT=5 I should not get the following:
     ATOMIC SPIN POPULATION (ALPHA MINUS BETA)^M
      ATOM         MULL.POP.                    LOW.POP.^M
   1 C             0.000553                     0.001053^M
   2 C             0.000553                     0.001064^M
   3 C             0.000553                     0.001059^M
   4 S             0.019501                     0.022770^M
   5 S             0.019501                     0.023763^M
   6 S             0.019501                     0.024020^M
   7 H             0.000156                     0.000189^M
   8 H             0.000156                     0.000193^M
   9 H             0.000156                     0.000190^M
  10 H             0.000234                     0.000437^M
  11 H             0.000234                     0.000435^M
  12 H             0.000234                     0.000435^M
  13 H             0.000018                     0.000107^M
  14 H             0.000018                     0.000109^M
  15 H             0.000018                     0.000109^M
  16 S             0.084614                     0.082322^M
  17 S             0.084614                     0.082302^M
  18 S             0.084614                     0.082187^M
  19 S             0.169856                     0.165213^M
  20 FE            1.171638                     1.168556^M
  21 FE            1.171638                     1.171346^M
  22 FE            1.171638                     1.172142^M

But I should obtain +5 -5 and +4 at three irons.. or like this. How can I validate that it is true? Is there some experimental results that say that spin density at iron atoms of Fe-S clusters should be such assymmetric?


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