Hello eveyone,
Summary: I found a curious result when running a Counterpoise (CP) corrected Hessian for a known global minimum structure. The projected Hessian differ significantly from the unprojected results, something that did not happen without CP.
Context: I made a second-derivative run at a global minimum structure (C_2h point group symmetry) which was optimized at the Frozen-Core CCSD(T)/aug-cc-pVDZ level (using other quantum package).
- This is supposed to be a minimum (thought it may not be at this level of theory).
- The imaginary frequency is very large, even if this stationary point, at this level of theory, is a first-order TS.
- Since the forces should be zero, before and after the projection the frequencies should be the same, which was the case when no counterpoise correction was included in the job. What surprised me the most is that the nuclear repulsion energy and the electronic energy computed by PSI4 are “exactly” the same as the ones I obtained with the other quantum package.
Input:
#counterpoise vibfreq
psi4.set_memory(‘50 GB’)
psi4.set_num_threads(10)
dimer = psi4.geometry(“”"
0 1
C 0.0000000000 0.6890807464 0.9171748908
O 0.0000000000 0.0000000000 0.0000000000
0 1
C 0.0000000000 -0.6890807457 4.3410689806
O 0.0000000000 0.0000000000 5.2582438714
units angstrom
“”")
psi4.set_options({
“basis”: “AUG-CC-PVDZ”,
“freeze_core”: True,
“scf_type”: “pk”
})
psi4.frequency(‘ccsd(t)’, bsse_type = ‘cp’, molecule=dimer, return_wfn=True)
Output:
==> N-Body: Counterpoise Corrected (CP) energies <==
n-Body Total Energy Interaction Energy N-body Contribution to Interaction Energy
[Eh] [Eh] [kcal/mol] [Eh] [kcal/mol]
1 -226.148105592093 0.000000000000 0.000000000000 0.000000000000 0.000000000000
FULL/RTN 2 -226.148590186506 -0.000484594413 -0.304087585344 -0.000484594413 -0.304087585344
==> Harmonic Vibrational Analysis <==
non-mass-weighted Hessian: Symmetric? True Hermitian? True Lin Dep Dim? 3 (0)
projection of translations (True) and rotations (True) removed 6 degrees of freedom (6)
total projector: Symmetric? True Hermitian? True Lin Dep Dim? 6 (6)
mass-weighted Hessian: Symmetric? True Hermitian? True Lin Dep Dim? 3 (0)
pre-proj low-frequency mode: 0.0000i [cm^-1]
pre-proj low-frequency mode: 0.0000i [cm^-1]
pre-proj low-frequency mode: 0.0000 [cm^-1]
pre-proj low-frequency mode: 0.0000 [cm^-1]
pre-proj low-frequency mode: 2.2855 [cm^-1]
pre-proj low-frequency mode: 2.3337 [cm^-1]
pre-proj low-frequency mode: 11.9213 [cm^-1]
pre-proj low-frequency mode: 23.9077 [cm^-1]
pre-proj low-frequency mode: 25.4804 [cm^-1]
pre-proj low-frequency mode: 69.4484 [cm^-1]
pre-proj all modes:[‘94.3053i’ ‘0.0000i’ ‘0.0000’ ‘0.0000’ ‘2.2855’ ‘2.3337’ ‘11.9213’
‘23.9077’ ‘25.4804’ ‘69.4484’ ‘2104.1167’ ‘2105.6230’]
projected mass-weighted Hessian: Symmetric? True Hermitian? True Lin Dep Dim? 6 (6)
post-proj low-frequency mode: 94.3053i [cm^-1] (V)
post-proj low-frequency mode: 0.0000i [cm^-1] (TR)
post-proj low-frequency mode: 0.0000i [cm^-1] (TR)
post-proj low-frequency mode: 0.0000i [cm^-1] (TR)
post-proj low-frequency mode: 0.0000i [cm^-1] (TR)
post-proj low-frequency mode: 0.0000 [cm^-1] (TR)
post-proj low-frequency mode: 0.0000 [cm^-1] (TR)
post-proj low-frequency mode: 23.8892 [cm^-1] (V)
post-proj low-frequency mode: 25.4769 [cm^-1] (V)
post-proj low-frequency mode: 69.4474 [cm^-1] (V)
post-proj all modes:[‘94.3053i’ ‘0.0000i’ ‘0.0000i’ ‘0.0000i’ ‘0.0000i’ ‘0.0000’ ‘0.0000’
‘23.8892’ ‘25.4769’ ‘69.4474’ ‘2104.1167’ ‘2105.6230’]
Vibration 1 8 9
Freq [cm^-1] 94.3053i 23.8892 25.4769
Irrep Au
Reduced mass [u] 13.4388 13.4388 14.6891
Force const [mDyne/A] -0.0704 0.0045 0.0056
Turning point v=0 [a0] 0.0000 0.6124 0.5672
RMS dev v=0 [a0 u^1/2] 0.0000 1.5874 1.5372
Char temp [K] 0.0000 34.3712 36.6557
1 C 0.45 -0.34 0.00 0.00 -0.00 0.57 0.10 0.39 0.00
2 O -0.34 0.26 0.00 0.00 -0.00 -0.42 -0.13 0.57 -0.00
3 C 0.45 -0.34 -0.00 -0.00 0.00 0.57 -0.11 -0.39 0.00
4 O -0.34 0.25 0.00 -0.00 0.00 -0.42 0.13 -0.57 -0.00