CCL:G: G03-Excessive mixing of frozen core and valence orbitals

 Sent to CCL by: "Shobe, David" [David.Shobe|-|sud-chemie.com]
 Ding,
 The Mulliken charges you see on H #7 and F #8 are related to the error message
 you got earlier.  It just means that the basis functions on H #7 and F #8 are
 being occupied in the calculation.
 What bothers me is the charge of > +7 on F #4.   This means that the valence
 orbitals on F #4 are NOT being used in the wave function!!!  You might want to
 look at the electron density (if you have a suitable visuialization program) to
 see whether that is strange also.   Do you get similar Mulliken charges in a HF
 calculation?  What about other types of charges (NBO, CHELPG, etc.)?
 Regards,
 --David Shobe
 -----Original Message-----
 > From: owner-chemistry*ccl.net [mailto:owner-chemistry*ccl.net]
 Sent: Tuesday, February 20, 2007 2:59 AM
 To: Shobe, David
 Subject: CCL:G: G03-Excessive mixing of frozen core and valence orbitals
 Sent to CCL by: Xunlei Ding [dingxunlei:gmail.com] Dear David,
 Thank you very much for your clear explain and suggestions.
 If this work is done with mp2(fc)/6-311++G**, the error is the same:
 " Largest valence mixing into a core orbital is  9.94D-01 Excessive mixing
 of frozen core and valence orbitals."
 And it finishes successfully with mp2=full, but the energy is very strange, and
 also the mulliken charge:
   Mulliken atomic charges:
                1
       1  H   -1.463786
       2  F   -0.398420
       3  H   -0.625697
       4  F    7.487903
       5  H   -1.463786
       6  F   -0.398420
       7  H   -1.625697
       8  F   -1.512097
 Also mp2(full)/6-311++G** gives strange energy and mulliken charge.
 If the work is done with counterpoise=2 or massage, as suggested by Douglas Fox,
 everything seems ok (both basis sets, and both mp2-full and mp2-fc). So maybe it
 is a problem of -bq.
 Best regards!
 Ding
 Shobe, David David.Shobe---sud-chemie.com wrote:
 >Sent to CCL by: "Shobe, David" [David.Shobe=sud-chemie.com]
 Because you
 >are using ghost atoms, there are empty core orbitals.  The HF routine does
 not distinguish core orbitals from valence orbitals (at least I think this is
 true), but the MP2 defaults to MP2=FC (frozen core) which of coures does make
 the distinction.  Note that 9.92D-01 = 0.992 = almost full occupancy!
 >
 >Perhaps using mp2=full would help, but then you'd have to redo any other mp2
 calculations (you have to be consistent: either mp2=full everywhere or mp2=fc
 everywhere).
 >
 >A larger basis set like 6-311+G* or aug-cc-pVTZ is likely to improve
 matters.  With more valence orbitals to choose from, there is less need to use
 the core orbital.  The 6-31G* basis set is too small for accurate calculations
 of hydrogen bonding energies anyway, if that's what you're after.  Again, you'd
 have to redo any calculations you've already performed using the smaller basis
 set.
 >
 >Regards,
 >--David Shobe
 >  Süd-Chemie, Inc.
 >
 >Attention to detial is essentail.
 >
 >
 >-----Original Message-----
 >
 >
 >>From: owner-chemistry=-=ccl.net [mailto:owner-chemistry=-=ccl.net]
 >>
 >>
 >Sent: Sunday, February 18, 2007 8:39 PM
 >To: Shobe, David
 >Subject: CCL:G: G03-Excessive mixing of frozen core and valence
 >orbitals
 >
 >
 >Sent to CCL by: Ding Xunlei [dingxunlei^-^gmail.com] Dear All,
 >
 >I did a calculation using mp2 and I find an error below.
 >Could you give me some suggestion? Thank you!
 >
 >This input file:
 >------------------------------------------------------------
 >#mp2/6-31G*
 >
 >test
 >
 >0 1
 >            H           0.000000   -0.917747    0.000000
 >            F           0.000000    0.000000    0.000000
 >            H           0.000000    1.956639    0.000000
 >            F           0.000000    2.875828    0.000000
 >            H           0.000000   -0.917747   -2.250000
 >            F           0.000000    0.000000   -2.250000
 >            H-bq        0.000000    1.956639   -2.250000
 >            F-bq        0.000000    2.875828   -2.250000
 >
 >------------------------------------------------------------
 >
 >The output file:
 >-------------------------------------------------------------------
 > SCF Done:  E(RHF) =  -199.305447100     A.U. after   21 cycles
 >             Convg  =    0.2272D-08             -V/T =  1.9654
 >             S**2   =   0.0000
 > ExpMin= 1.61D-01 ExpMax= 7.00D+03 ExpMxC= 1.05D+03 IAcc=1 IRadAn=
 >    1 AccDes= 1.00D-06
 > HarFok:  IExCor= 205 AccDes= 1.00D-06 IRadAn=         1 IDoV=1
 > ScaDFX=  1.000000  1.000000  1.000000  1.000000  Largest valence mixing
 into a core orbital is  9.92D-01  Excessive mixing of frozen core and valence
 orbitals.
 > Error termination via Lnk1e in /gaussian/03d02-xlf10/g03/l801.exe at Sat
 Feb 17 16:37:03 2007.
 >
 >
 >Yours sincerely,
 >Ding Xunlei
 >2007-02-19
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