[molpro-user] The smallest exponent that can be used to specify a basis function

[Gerald Knizia]

Dear Tatiana,
yes, there seems to be a bug somewhere down in the seward integral path:
It works with exponent 0.501e-12, but blows up with 0.500e-12. If I find
some time I'll look up what exactly is happening.

As a temporary work around, it is possible to use the argos integral
program instead (see attachment). With this an exponent of 1e-30 works
just fine if turning down the thresholds.

Thanks again for pointing out this trick for emulating IP/EA-EOM-CCSD. I
didn't know this one.
-- 
Gerald Knizia

On Sat, 2013-05-11 at 19:59 +0200, Tatiana Korona wrote:
> Dear Gerald,
> 
> A gaussian with the exponent equal to 1.E-50 has been used by Stanton and Gauss 
> to obtain IP-EOM-CC3 energies directly from an EE-EOM-CC3 program, see 
> J.Chem.Phys.,111,8785,1999, and ref. 18 there. If it were excluded by the 
> program, then they wouldn't be able to calculate ionization potentials and make 
> numbers for that paper. So, such a small exponent is certainly possible and 
> _active_ in the program they used (probably Aces). I repeated this trick to 
> obtain IP and EA with Molpro, but could use only the exponents like 1.E-12 for a 
> continuum orbital. However, one can verify that this exponent is enough to 
> provide a sufficient number of accurate digits for ionization potentials and 
> electron attachments, e.g. I reproduced all digits given in papers on EA-EOM-CC 
> methods.
> 
> You can test the following simple input
> 
> ***, IP-EOM-CCSD (simulated with EE-EOM-CCSD)
> memory,20,m
> 
> gprint,basis,orbital=10
> zsymel=nosym
> basis={
> default,H=avdz,O=avdz
> s,O,1.e-12
> }
> geometry={H1
>            O,H1,R,              !Z-matrix for water
>            H2,O,R,H1,THETA}
> Theta=104                    !start bond angle
> R=0.96 Ang                   !start bond distance
> 
> hf
> ccsd
> eom,-5.1,vir_orb=6.1 ! fix on excitations TO this orbital
> 
> This input will produce first 4 IPs for water. 6.1 is our zero-energy continuum 
> orbital. However, if you change an additional exponent on oxygen from 1.e-12 to 
> e.g. 1.e-15 or smaller, than you will get:
> 
>   ITERATION    DDIFF          GRAD             ENERGY        2-EL.EN. 
> DIPOLE MOMENTS         DIIS   ORB.
>      1      0.000D+00      0.000D+00     32025.50226135  64244.652599        NaN 
> NaN        NaN    0    start
>      2      0.000D+00      0.232D+02       -16.95078177     84.371664        NaN 
> NaN        NaN    1    diag
>      3      0.187D+02      0.165D+00     32657.17607612  65469.453071        NaN 
> NaN        NaN    2    diag
>      4      0.209D+02      0.106D+02     32655.12447108  65465.460273        NaN 
> NaN        NaN    3    diag
>      5      0.433D-01      0.108D+02     32649.67192410  65454.845120        NaN 
> NaN        NaN    4    diag
>   ?TOTAL ENERGY UNREASONABLE, ETOT =         0.32650D+05, ENEST = 
> -0.75852D+02
> 
> in Hartree-Fock.
> 
> Best wishes,
> 
> Tatiana
> 
> On Sat, 11 May 2013, Gerald Knizia wrote:
> 
> >
> > On Wed, 2013-05-08 at 11:41 +0200, Evgeniy Gromov wrote:
> >> Gamess-US can converge SCF "hands down" with an exponent 1.E-50 .
> >> Molpro however could do the same with 1.E-10. 1.E-15 or smaller
> >> didn't work :(
> >
> > Unlike other programs, Molpro never throws away basis functions if they
> > become unreasonable. Are you sure that your 1e-50 exponent basis
> > function actually ended up the calculation? Because for such a function
> > even handling its normalization coefficient would be a serious problem.
> >
> > While it is perfectly possible to calculate integrals over such
> > functions[1] (it is even done routinely with zero exponent functions for
> > implementing simpler integrals in terms of more complicated integrals),
> > using them as basis functions is very much not recommended. If you want
> > to try it anyway, be sure to turn off all integral screening,
> > compression, and approximation options.
> >
> > [1] See JCTC 7 2387 (2011)
> > -- 
> > Gerald Knizia
> >
> > _______________________________________________
> > Molpro-user mailing list
> > Molpro-user at molpro.net
> > http://www.molpro.net/mailman/listinfo/molpro-user
> >
> 
> 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
> 
> 
> `The man who makes no mistakes does not usually make anything.'
>                                         Edward John Phelps (1822-1900)

-------------- next part --------------
***, IP-EOM-CCSD (simulated with EE-EOM-CCSD)
! original from Tatiana Korona, Sat May 11, 2013
memory,20,m

gprint,basis,orbital=10
zsymel=nosym
basis={
default,H=avdz,O=avdz
! s,O,0.501e-12 ! works with seward
s,O,0.500e-30 ! doesn't work with seward, but does with argos.
}
geometry={H1
          O,H1,R,              !Z-matrix for water
          H2,O,R,H1,THETA}
Theta=104                    !start bond angle
R=0.96 Ang                   !start bond distance


{gthresh,oneint=1e-40,twoint=1e-40,prefac=1e-40}
intp
! ^- explicitly call argos integral program, as a work-around. Seward apparently
!    does something funky. It works just fine with an exponent of 0.501e-12, but
!    doesn't with 0.500e-12. Should probably look up what exactly that is...
!                                                - Gerald Knizia

hf
ccsd
eom,-5.1,vir_orb=6.1 ! fix on excitations TO this orbital