Does 43-ccd.py work for CCD analytic gradients? #1918
Description
The script examples/cc/43-ccd.py offers a simple solution to calculate the CCD energy using CCSD code. If mc.Gradients() is appended to calculate the CCD analytic gradients, will the results be correct?
I've performed such a calculation using different quantum chemistry packages, and I find that CCD analytic gradients of PySCF are somewhat different from those of other packages. This is my input script
h2o_rhf.zip
Here are the last few lines in the script
mc = cc.CCSD(mf)
mc.verbose = 4
mc.frozen = 0
old_update_amps = mc.update_amps
def update_amps(t1, t2, eris):
t1, t2 = old_update_amps(t1, t2, eris)
return t1*0, t2
mc.update_amps = update_amps
mc.kernel()
from pyscf import grad
mcg = mc.Gradients()
mcg.max_memory = 4000 # MB
mcg.kernel()
Here are the CCD/cc-pVTZ analytic gradients from 3 packages (no frozen core):
(1) Gaussian
0.00000000E+00 0.00000000E+00 -4.16132400E-03
0.00000000E+00 -1.17245720E-02 2.08066200E-03
0.00000000E+00 1.17245720E-02 2.08066200E-03
(2) CFOUR
0.00000000E+00 1.10000000E-14 -4.16106176E-03
0.00000000E+00 -1.17247788E-02 2.08053088E-03
0.00000000E+00 1.17247788E-02 2.08053088E-03
(3) PySCF
0.00000000E+00 0.00000000E+00 -4.63005710E-03
0.00000000E+00 -1.14598343E-02 2.31502860E-03
0.00000000E+00 1.14598343E-02 2.31502860E-03
Maybe there is some code to be modified regarding solving the lambda equation? Thanks for any help or suggestion.