[molpro-user] E2exdisp in CCSD-SAPT converges to the wrong value in DC+BS

[Leonid Shirkov]

Dear Tatiana,

thank you for the helpful reply.
Insertion of  "dummy,be1dummy" before the first part of the calculation
did resolve the problem.

These sample inputs provide the CCSD(3) approximation, do they?
Is there any way to use the CCSD(2) and CCSD(4) ones in Molpro?

Best regards,
Leonid

On Thu, Sep 22, 2016 at 4:49 PM, Tatiana Korona
<tania at tiger.chem.uw.edu.pl> wrote:
> Dear Leonid,
>
> my result for your no-df input with one line modification gives:
>
> E2disp=-2.907495
> E2exdisp=0.473707
>
> You have not set your artificial beryllium atom to dummy before the first
> part of the calculation, therefore a wrong Enuc has been found for the
> dimer.
>
> This was the main problem present in both inputs.
>
> Additionally, for the DF case you should provide a more sensible auxiliary
> basis set on dummy. Note that an auxiliary basis should describe PRODUCTS of
> the atomic basis.
>
> Best wishes,
>
> Tatiana
>
>
> On Thu, 22 Sep 2016, Leonid Shirkov wrote:
>
>> Hello Molpro Community,
>>
>> I was running some test jobs to calculate E2disp and E2exdisp energies
>> for He2 with
>> CCSD-SAPT at R=3.0 bohrs  (interatomic distance).  In order to speed
>> up the convergence
>> I employed midbond functions, and that works well for E2disp. However,
>> E2exdisp converges
>> to a smaller wrong value if DC+BS is used. Without the midbond
>> functions, i.e. with DCBS,
>> it converges to a value that  agrees well with  the previously
>> reported CCSD-SAPT calculations,
>> see 10.1063/1.2889006 and  10.1021/ct900232j.
>> These values are Edisp=2.937 and E2exdisp=0.479 (mhartree units).
>>
>> Here is the outline of the results, '+' denotes the midbond functions,
>>
>> without density-fitting:
>>
>>             Edisp  Eexdisp
>> avtz       -2.599   0.391
>> avdz+    -2.884   0.165
>> avtz+     -2.907   0.235
>> avqz+    -2.940   0.261
>>
>> with density-fitting (avXz/mp2fit used as the auxilary basis set):
>>
>>           Edisp  Eexdisp
>> avtz     -2.600   0.383
>> avqz    -2.853   0.454
>> avdz+  -2.894   0.087
>> avtz+   -2.910   0.103
>> avqz+  -2.937   0.115
>>
>> I am attaching the inputs that I used for DC+BS calculations, both df
>> and non-df versions.
>> Is there anything wrong with my inputs? Perhaps some input parameters
>> or thresholds ought
>> to be tweaked? Increasing the integration grid by the 'dispgg' parameter
>> to
>> 20 does not help. Just in case it matters, I am using the 2012.1 version.
>>
>> I would appreciate any help and insight.
>>
>> Leonid
>>
>
> Dr. Tatiana Korona http://tiger.chem.uw.edu.pl/staff/tania/index.html
> Quantum Chemistry Laboratory, University of Warsaw, Pasteura 1, PL-02-093
> Warsaw, POLAND
>