I am new to DFT and NWChem and am having difficulties using range-separated functionals for the C70 fullerene (which is like a buckyball except more oval-shaped). If I use the more conventional functional B3LYP, I have no trouble with "task dft" or "task dft optimize" for this system. However, once I attempt a range-separated functional such as BNL or CAM-B3LYP, the energy blows up immediately and the calculation never converges.
I have tried the following, without success:
-Adding damping, up to 98%, for all iterations.
-Using a geometry that was optimized with B3LYP and using the molecular orbitals from the B3LYP calculation as input for the range-separated calculation.
The energy goes wild immediately, with the second iteration having an energy 100 times larger than the first iteration.
I have pasted the input file below. I would be very grateful for any thoughts on using range-separated functionals for this system.
title "C70"
echo
geometry units angstroms
symmetry d5h
C -0.367687664 1.131626269 3.870162242
C -0.733827376 2.258488433 -3.127084897
C -1.920025931 2.253477156 -2.387939803
C -1.694377302 2.945472037 -1.197698888
C -2.325526743 2.568975024 0.000000000
end
basis
carbon library 6-311G*
end
dft
xc xcamb88 1.00 lyp 0.81 vwn_5 0.19 hfexch 1.00
cam 0.33 cam_alpha 0.19 cam_beta 0.46
direct
vectors input C70_from_b3lyp.movecs output C70.movecs
print "information"
iterations 200
convergence ncydp 200
convergence damp 98
end
scf
semidirect memsize 100000000 filesize 0
end
memory total 8000 stack 2000 heap 2000 global 4000 mb
task dft optimize
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