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,
On Wed Apr 6 '16 10:07pm, Alex Granovsky wrote
>Search this site on "mp4(d)" returns these two useful threads:
>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
>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.
>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