wrong ovos-ccsdt gradient

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1 year 2 months ago #1153 by huangbi
Dear mrcc users/developers,

When using 
ovirt=ovos (ovosnorb=50)
to speed up ccsdt calculations, the final dipole & molecular gradient seem to be totally wrong. Take H2 for example, these are the results:

[with ovos]
 Molecular gradient [au]:
    1  H      0.0449345831     0.0004366843     0.2871843142
    2  H     -0.0449345831     0.0004366843    -0.2871843142
 Dipole moment [Debye]:        0.02476652
   x=     -0.00024495  y=     -0.02438433  z=      0.00432724

while the reasonable ones are [no use of ovirt]:
 Molecular gradient [au]:
    1  H      0.0000000000     0.0000000000     0.0000531176
    2  H      0.0000000000     0.0000000000    -0.0000531176
 Dipole moment [Debye]:        0.00000000
   x=      0.00000000  y=      0.00000000  z=     -0.00000000

The computed energies by ovos scheme are very close to those without truncation of virtual space though, and the equilibrium H2 distance is verified by scanning the distances.

I suspect that the code fails to transform from optimized virt space to MO space. This issue exists for both 2019 & 2020 version of binary mrcc. Any idea?

Best,
Bing

PS: here is my input
=======================
mem=120GB
mpitasks=1
basis=cc-pCV6Z
#scfiguess=mo #restart
scftype=rhf
calc=ccsdt
ccprog=mrcc
ovirt=ovos
ovosnorb=50
dens=2
charge=0
mult=1
geom=xyz
2
Exp.
H 0. 0. 0.
H 0. 0. 0.7414
 

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1 year 2 months ago #1154 by kallay
Replied by kallay on topic wrong ovos-ccsdt gradient
Dear Bing,
Unfortunately, CC gradients are not implemented with the OVOS approximation.

Best regards,
Mihaly Kallay

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1 year 2 months ago #1155 by huangbi
Replied by huangbi on topic wrong ovos-ccsdt gradient
Thanks for your prompt reply!

Maybe it helps to make mrcc display some warning message or simply terminate when both ovos & dens=2 are given as input...

Best,
Bing

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1 year 2 months ago #1156 by huangbi
Replied by huangbi on topic wrong ovos-ccsdt gradient
Can one trust the resulting 2RDM? It seems that energy from 2RDM (see below) in the case of ovirt=ovos is correct. But the associated dipole moment is totally wrong. I'm puzzled! Any idea?

ovirt=ovos; ovosnorb=50
Total CCSDT energy [au]: -1.174253395035
Total energy from RDM [au]: -1.174253395062
Dipole moment [Debye]: 0.02476652

ovirt=off
Total CCSDT energy [au]: -1.174345651956
Total energy from RDM [au]: -1.174345652024
Dipole moment [Debye]: 0.00000000

Best,
Bing

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1 year 2 months ago #1157 by kallay
Replied by kallay on topic wrong ovos-ccsdt gradient
Yes, you can. The 1RDM and 2RDM are the correct unrelaxed RDMs. The properties are wrong.

Best regards,
Mihaly Kallay

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1 year 2 months ago #1158 by huangbi
Replied by huangbi on topic wrong ovos-ccsdt gradient
Good to know!

BTW, Is there any keyword control for computing unrelaxed rdm2 only, without carrying on to property calc in the case of dens=2?

best,
Bing

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