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12:22:08 PM PDT  Mon, Oct 17th 2011 

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 selfexchange 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
Oneelectron contribution H1(RP) 0.0040314092
Twoelectron integral screening (tol2e) : 6.03E11
Twoelectron contribution H2(RP) 0.0007837138
Total interaction energy H(RP) 0.0032476955
Electron Transfer Coupling Energy V(RP) 0.0000254810
5.592 cm1
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
Oneelectron contribution H1(RP) 4.6181893392
Twoelectron integral screening (tol2e) : 6.03D11
Twoelectron contribution H2(RP) 1.4262407635
Total interaction energy H(RP) 3.1919485757
Electron Transfer Coupling Energy V(RP) 2.1006474897
461038.768 cm1
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
Oneelectron contribution H1(RP) 4.3005260783
Twoelectron integral screening (tol2e) : 6.03D11
Twoelectron contribution H2(RP) 1.3467663226
Total interaction energy H(RP) 2.9537597556
Electron Transfer Coupling Energy V(RP) 0.7327601032
160822.231 cm1
19.939428 eV
459.814 kcal/mol
Although the trend is as expected (coupling goes down with distance; @ tol2e=default 1e7, 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 6.03e11
vectors reactants HeA.movecs
vectors products HeB.movecs
end
task scf et




Bert Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop


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Threads 2
Posts 285


12:52:48 PM PDT  Mon, Oct 17th 2011 

An overlap between the reactant and product being 1 obviously means that the orbitals for both the reactant and product are the same, i.e. the electron has not been moved from one atom to the other. You can easily check this by looking at the changes and populations at the end of the reactant and product SCF runs. The following input deck works fine for me.
Bert
start chang
ECHO
TITLE "Test for ET module os NWChem"
basis "ao basis" cartesian
* library "Ahlrichs_pVDZ"
end
geometry
He 0 0 0
end
charge 1
scf
uhf
doublet
vectors output HeP.movecs
end
task scf
charge 0
scf
uhf
singlet
vectors output He.movecs
end
task scf
geometry noautosym noautoz
He 0.0 0.0 0.0
He 5.0 0.0 0.0
end
charge 1
 ET reactants:
scf
doublet; uhf; vectors input fragment HeP.movecs He.movecs output HeA.movecs
end
task scf
 ET products:
scf
doublet; uhf; vectors input HeA.movecs reorder 2 1 output HeB.movecs
end
task scf
et
vectors reactants HeA.movecs
vectors products HeB.movecs
end
task scf et
Quote:Cchang Oct 17th 7:22 pmI've been seeing some very large couplings when running the et task, and so I decided to try the example in the manual, a selfexchange 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
Oneelectron contribution H1(RP) 0.0040314092
Twoelectron integral screening (tol2e) : 6.03E11
Twoelectron contribution H2(RP) 0.0007837138
Total interaction energy H(RP) 0.0032476955
Electron Transfer Coupling Energy V(RP) 0.0000254810
5.592 cm1
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
Oneelectron contribution H1(RP) 4.6181893392
Twoelectron integral screening (tol2e) : 6.03D11
Twoelectron contribution H2(RP) 1.4262407635
Total interaction energy H(RP) 3.1919485757
Electron Transfer Coupling Energy V(RP) 2.1006474897
461038.768 cm1
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
Oneelectron contribution H1(RP) 4.3005260783
Twoelectron integral screening (tol2e) : 6.03D11
Twoelectron contribution H2(RP) 1.3467663226
Total interaction energy H(RP) 2.9537597556
Electron Transfer Coupling Energy V(RP) 0.7327601032
160822.231 cm1
19.939428 eV
459.814 kcal/mol
Although the trend is as expected (coupling goes down with distance; @ tol2e=default 1e7, 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 6.03e11
vectors reactants HeA.movecs
vectors products HeB.movecs
end
task scf et





5:00:44 PM PDT  Tue, Oct 18th 2011 

Hi Bert,
Thanks, I could get it with your deck. I figured the overlap was symptomatic of the problem, but I was expecting an Inf (or stars) coupling if the overlap were really 1.0 between the reactant and product wavefunctions. It came down to requiring "noautosym" to be present. Now I see, symmetrizing the wavefunctions forced the solutions to delocalize despite the localized fragment guess.
Thanks again!



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