I may have found an issue with the CIS/TDA gradient (which possibly is also present in the full TDDFT). Version is Nwchem-6.5.revision26243-src.2014-09-10 with the Parallelmpi.patch applied. Consider the following input:
ECHO
PRINT DEBUG
START temp
TITLE "gradient calc"
GEOMETRY units au noautoz
symmetry c1
Be 0.0 0.0 0.0
Be 1.0 0.0 0.0
H 0.0 0.0 0.7
H 1.0 0.2 -0.6
END
BASIS "ao basis" PRINT spherical
Be S
936.8902499 0.0091636
171.7778018 0.0493615
48.0572387 0.1685383
16.5089585 0.3705628
6.4109117 0.4164915
2.6403675 0.1303341
Be S
19.0644035 0.0091636
3.4954375 0.0493615
0.9778975 0.1685383
0.3359342 0.3705628
0.1304531 0.4164915
0.0537278 0.1303341
Be S
13.0509616 0.0091636
2.3928795 0.0493615
0.6694415 0.1685383
0.2299712 0.3705628
0.0893046 0.4164915
0.0367805 0.1303341
H S
33.2683653 0.0091636
6.0997184 0.0493615
1.7064814 0.1685383
0.5862224 0.3705628
0.2276473 0.4164915
0.0937577 0.1303341
END
DFT
XC HFexch 1.0
END
TDDFT
CIS
NROOTS 5
NOTRIPLET
thresh 1e-5
TARGET 1
CIVECS
PRINT DEBUG
FREEZE virtual 2
GRAD
ROOT 1
PRINT DEBUG
END
END
TASK TDDFT GRADIENT
A rather strange but well-behaved molecule with some frozen virtuals.
The resulting NWCHEM analytical gradient is:
atom coordinates gradient
x y z x y z
1 Be -0.500000 -0.020000 -0.010000 7.274093 0.804309 5.306119
2 Be 0.500000 -0.020000 -0.010000 -7.226557 3.004583 -6.231942
3 H -0.500000 -0.020000 0.690000 1.220940 -0.550613 -6.921864
4 H 0.500000 0.180000 -0.610000 -1.268477 -3.258278 7.847687
By changing the task line to
TASK TDDFT GRADIENT numerical
I obtain the NWCHEM numerical gradient:
atom coordinates gradient
x y z x y z
1 Be -0.500000 -0.020000 -0.010000 7.294946 0.808334 5.284754
2 Be 0.500000 -0.020000 -0.010000 -7.252036 3.003535 -6.211470
3 H -0.500000 -0.020000 0.690000 1.211833 -0.557386 -6.885883
4 H 0.500000 0.180000 -0.610000 -1.254743 -3.254483 7.812599
Note the deviations in the second decimal place. I would consider this high, so high in fact, that I believe to have found a bug. Calculations using ORCA confirm this.
Consider the ORCA numerical gradient:
The cartesian numerical gradient:
---------------------------------
1 Be : 7.292673109 0.809276482 5.284813140
2 Be : -7.250520943 3.004624398 -6.211909732
3 H : 1.212733473 -0.558310659 -6.886530418
4 H : -1.254885640 -3.255590221 7.813627010
and the analytical counterpart:
CARTESIAN GRADIENT
------------------
1 Be : 7.292401418 0.809317573 5.284476022
2 Be : -7.250268956 3.004906532 -6.211600815
3 H : 1.212702264 -0.558350628 -6.886268442
4 H : -1.254834726 -3.255873477 7.813393235
Concerning the settings, I am confident to have performed the freezing correctly in both programs, given that I obtain the following excitation energies:
NWCHEM ORCA
0.147882333 0.147883
0.567416779 0.567417
1.182899967 1.182900
4.676393656 4.676394
5.899078825 5.899079
In any event, the numerical vs. analytical discrepancies of NWCHEM seem high. It would be great if someone could confirm the issue.
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