Dipole moment

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4 years 2 months ago #262 by tamas821
Replied by tamas821 on topic Dipole moment
Dear Professor Kállay,

I recently returned to the matter of computing the dipole moment values of H2He+ in its ground and excited electronic states, and would like to ask for your help in something I don't understand.
In my FCI/aug-cc-pVTZ calculations I found that the computed dipole moments for the first and second excited states behaved strange, i.e. they changed "discontinously" with respect to small changes in the nuclear distances.
Therefore, I made some test calculations to see what the issue might be. My question is about these test calculations. In my understanding, for H2He+ with three electrons, the FCI and CCSDT methods should be the same in principle. But when comparing FCI/cc-pVDZ and CCSDT/cc-pVDZ computations, I find a huge difference in the dipole moments of the excited electronic states:
FCI/cc-pVDZ
Energy -3.488512899 dipole 0 0 0.00560133
Energy -3.126094303 dipole 0 0 -0.00893903

Energy -3.049118919 dipole 0 0 0.01723041
Energy -2.893181294 dipole 0 0 0.00205867
Energy -2.890695799 dipole 0 0 0.0234418

CCSDT/cc-pVDZ
Energy -3.488512899 dipole 0 0 0.00560132
Energy -3.126094303 dipole 0 0 -5.66094205

Energy -2.890695799 dipole 0 0.00000498 -5.83185399
Energy -2.713822633 dipole 0 -0.00001074 -5.58909303
Energy -2.713822633 dipole 0 -0.00001074 -5.58909304

For the ground state the two calculations are in perfect agreement, but for the excited states (with energies -3.126094303 and -2.890695799) the dipole values are very different. Can you please explain the origin of the differences?

Attached you can find the input and output files.

Many thanks in advance,
Tamás
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4 years 2 months ago #263 by kallay
Replied by kallay on topic Dipole moment
Dear Tamás,
Thank you very much for reporting this. Please edit mrcc.f, at the beginning of subroutine step insert the line
if(calc.eq.0.and..not.osc) ampfile=tfile
before line
if(osc.and.(l3route.or.d2route)) lamfile=lfile
At the middle of the routine insert the line
if(calc.eq.0.and..not.osc) file2=tfile
after line
if(qcc.eq.1) file2=ampfile
This will fix this problem.
Please also note that a CC excited state property calculation is only possible for one excited state at a time, but this is not true for CI. That is, you can set nstate=5 if a CI calculation is run, but if you use CC, you must run a separate calculation for each excited state with nstate=2.

Best regards,
Mihaly Kallay

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4 years 2 months ago #264 by tamas821
Replied by tamas821 on topic Dipole moment
Dear Professor Kállay,

thank you again for your prompt help, it solved the problem.

With warm regards,
Tamás

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