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David Shobe
avidshobe@yahoo.com

When you get the following error message
THE INPUT BASIS SET CONTAINS A LINEAR DEPENDENCE
it doesn't tell you which functions are redundant, unlike the case for a near linear dependence.  How do you know which functions to delete?

Thanks for you help so far,
--David


On Wed Apr 6 '16 10:07pm, Alex Granovsky wrote
----------------------------------------------
>Dear David,
>Dear Pedro,

>Search this site on "mp4(d)" returns these two useful threads:
>
>
>http://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C393fb1c3f2vS-7378-1007-00.htmhttp://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C393fb1c3f2vS-7378-1007-00.htm

>http://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C3d2d5e75bcsK-8577-846+00.htmhttp://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C3d2d5e75bcsK-8577-846+00.htm
>
>
>In brief, this job has almost linearly dependent basis set. As printed
>in the output file:
>
>
>

 THE OVERLAP MATRIX HAS    4 EIGENVALUES BELOW 1.1E-04
 THE SMALLEST OF THESE IS 1.35832E-09. 

>The eigenvalue of overlap matrix of 1.35832E-09 corresponds
>to a severe quasi-linear dependence.

>The sensitivity of MP4(D) term of the MP4 energy to the linear
>dependence in the AO basis set has been already discussed on this
>forum several times. The MP4(D) term is the most sensitive one
>because during its computation one needs to transform integrals and
>other quantities from AO to MO basis, then back from MO to AO,
>and finally from AO to MO again. Each transformation kills up to
>several significant digits of the result (more precisely,
>the number of digits lost is directly related to the condition
>number of the overlap matrix) if all orbitals (including virtual
>ones) are not computed very precisely. So in the worst case like
>this one, one can lost all significant digits.
>
>
>What to do?

>One need to delete some orbitals to increase the smallest
>eigenvalue of the overlap matrix.

>As output indicates, the most problematic orbital is:

>

   0.2857E-08   -    C   5  S,   SHELL  31,   AO   73

>i.e. the S part of the diffuse L shell on the atom C5

>I attached archive with modified input file as well as
>the corresponding output file. In the new input, the
>problematic orbital was removed by replacing L shell
>located on atom C5 by P shell. Otherwise, the $DATA
>group of the modified input is equivalent to the initial
>$DATA and $BASIS groups.

>I also increased ICUT and ITOL, and disabled fdiff.
>Finally, I tightened nconv to 6 as recommended in
>output.

>The smallest eigenvalue of overlap matrix is now:

>

 THE SMALLEST OF THESE IS 4.10644E-08.

>i.e. ca. 30 times better!
>
>
>As a result, we obtain:

>

 RESULTS OF MOLLER-PLESSET 4TH ORDER CORRECTION ARE

            E(RHF)       =      -191.5685568750

            E(D,2)       =        -0.6457464825
            E(MP2)       =      -192.2143033575

            E(D,3)       =        -0.0166674371
            E(D,2+3)     =        -0.6624139197
            E(MP3)       =      -192.2309707947

            E(S,4)       =        -0.0073886039
            E(D,4)       =        -0.0200238070
            E(D,2+3+4)   =        -0.6824377267
            E(T,4)       =        -0.0337953970
            E(R+Q,4)     =         0.0168396781
            E(SDTQ,4)    =        -0.0443681298
            E(SDTQ,2+3+4)=        -0.7067820495
            E(MP4-SDTQ)  =      -192.2753389245

>Hope this helps.

>Kind regards,
>Alex Granovsky
>
>
>
>
>
>
>
>
>On Mon Apr 4 '16 0:12am, David Shobe wrote
>------------------------------------------
>>Is this the correct MP4 energy for this molecule (1,3-pentadiyne)?

>> RESULTS OF MOLLER-PLESSET 4TH ORDER CORRECTION ARE

>>            E(RHF)       =      -191.5694925024

>>            E(D,2)       =        -0.6494633272
>>            E(MP2)       =      -192.2189558295

>>            E(D,3)       =         0.2696414733
>>            E(D,2+3)     =        -0.3798218539
>>            E(MP3)       =      -191.9493143563

>>            E(S,4)       =        -0.0517477560
>>            E(D,4)       =       -26.2790188653
>>            E(D,2+3+4)   =       -26.6588407192
>>            E(T,4)       =        -0.0344433158
>>            E(R+Q,4)     =         0.0171693598
>>            E(SDTQ,4)    =       -26.3480405772
>>            E(SDTQ,2+3+4)=       -26.7278624311
>>            E(MP4-SDTQ)  =      -218.2973549335
>>