I've been seeing some very large couplings when running the et task, and so I decided to try the example in the manual, a self-exchange reaction with He/He+ ([1]) with NWChem version 6.0. I tried two runs, one with the He 5 Angstroms apart, and one @ 10 Angstroms apart. Basis set was Ahlrichs_pVDZ, from the library.
I don't know what the geometry or basis were for the example given in the documentation. For reference the values are given as
Electronic energy of reactants H(RR) -5.3402392824
Electronic energy of products H(PP) -5.3402392824
Reactants/Products overlap S(RP) -0.0006033839
One-electron contribution H1(RP) 0.0040314092
Two-electron integral screening (tol2e) : 6.03E-11
Two-electron contribution H2(RP) -0.0007837138
Total interaction energy H(RP) 0.0032476955
Electron Transfer Coupling Energy |V(RP)| 0.0000254810
5.592 cm-1
0.000693 eV
0.016 kcal/mol
For 5 A, I see
Electronic energy of reactants H(RR) -3.1919485760
Electronic energy of products H(PP) -3.1919485759
Reactants/Products overlap S(RP) : 1.00D+00
One-electron contribution H1(RP) -4.6181893392
Two-electron integral screening (tol2e) : 6.03D-11
Two-electron contribution H2(RP) 1.4262407635
Total interaction energy H(RP) -3.1919485757
Electron Transfer Coupling Energy |V(RP)| 2.1006474897
461038.768 cm-1
57.161559 eV
1318.177 kcal/mol
For 10 A, I see
Electronic energy of reactants H(RR) -2.9537597557
Electronic energy of products H(PP) -2.9537597556
Reactants/Products overlap S(RP) : 1.00D+00
One-electron contribution H1(RP) -4.3005260783
Two-electron integral screening (tol2e) : 6.03D-11
Two-electron contribution H2(RP) 1.3467663226
Total interaction energy H(RP) -2.9537597556
Electron Transfer Coupling Energy |V(RP)| 0.7327601032
160822.231 cm-1
19.939428 eV
459.814 kcal/mol
Although the trend is as expected (coupling goes down with distance; @ tol2e=default 1e-7, the opposite happened), the couplings are much too large. Also, S=1, unlike the small negative number in the example.
Thanks for any help.
Input for the 5A job was:
start 8TNaEwO57SmBqwjO
permanent_dir /scratch/scratchdirs/cchang/8TNaEwO57SmBqwjO/perm
scratch_dir /scratch/scratchdirs/cchang/8TNaEwO57SmBqwjO/scr
ECHO
TITLE "Test for ET module os NWChem"
geometry He nocenter noautoz
He 0.0 0.0 0.0
end
geometry HeP nocenter noautoz
He 5.0 0.0 0.0
end
geometry HeHeP nocenter noautoz
He 0.0 0.0 0.0
He 5.0 0.0 0.0
end
basis "ao basis" cartesian
* library "Ahlrichs_pVDZ"
end
scf
singlet; uhf; vectors input atomic output He.movecs
end
charge 0
set geometry He
task scf
scf
doublet; uhf; vectors input atomic output HeP.movecs
end
charge 1
set geometry HeP
task scf
#ET reactants:
scf
doublet; uhf; vectors input fragment He.movecs HeP.movecs output HeA.movecs
end
set geometry HeHeP
task scf
#ET products:
scf
doublet; uhf; vectors input HeA.movecs reorder 2 1 output HeB.movecs
end
task scf
et
tol2e 6.03e-11
vectors reactants HeA.movecs
vectors products HeB.movecs
end
task scf et
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