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

 Sent to CCL by: "Abrash, Samuel" [sabrash]~[richmond.edu]
 Hi Ding,
 You'd said earlier that when you use MP2=full the job works but the Mulliken
 distributions don't make sense.  Its well known that the Mulliken distributions
 tend to fail when diffuse functions are included in the basis set.
 Best,
 Sam
 -----Original Message-----
 > From: owner-chemistry*o*ccl.net [mailto:owner-chemistry*o*ccl.net]
 Sent: Tuesday, February 20, 2007 2:33 AM
 To: Abrash, Samuel
 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 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 succeeds with mp2=full.
 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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