Dear respected forum members,
The halogen-bonded F-F…NCNa complex was fully optimized at MP2/aug-cc-pVTZ level. Then the value of counterpoise-corrected interaction energy (CP-IE) was estimated through CCSD(T)/CBS approach of PSI4 employing “aug-cc-pV[TQ]Z” basis sets. The input file of CBS calculation is as follows (I use PSI4 1.5a1.dev117):
memory 55 gb
molecule dimer {
0 1
F 0.00000000 0.00000000 -3.65247200
F 0.00000000 0.00000000 -2.23792300
0 1
N 0.00000000 0.00000000 0.32488100
C 0.00000000 0.00000000 1.50710700
Na 0.00000000 0.00000000 3.79061400
units angstrom
no_reorient
symmetry c1
}
set {
freeze_core true
cc_type df
}
energy(cbs,scf_wfn=‘scf’,scf_basis=‘aug-cc-pV[TQ]Z’,scf_scheme=scf_xtpl_karton_2,corl_wfn=‘ccsd(t)’, corl_basis=‘aug-cc-pv[TQ]z’,corl_scheme=corl_xtpl_helgaker_2,bsse_type=[‘cp’,‘nocp’],scf_alpha=5.79,corl_alpha=3.05)
Very surprisingly and highly unexpectedly, the CP-IE for this complex is a large positive value of 58.04 kcal/mol!! indicating a quite destabilization. While F-F with a value of maximum electrostatic potential of V_s,max= 13.93 kcal/mol associated with “sigma-hole” of fluorine atom is not a very strong Lewis acid, the NCNa with a minimum electrostatic potential value of V_s,min= -64.77 kcal/mol corresponded to lone electron-pair of nitrogen atom is a strong Lewis base; thus, an almost strong F…N halogen bond interaction is expected. Or, at least, the value of CP-IE should never be positive.
I would be highly grateful if you let me know what is the origin of such a highly positive interaction energy and what solution is suggested. A part of the output is also respectfully presented at the end of this message.
Yours sincerely,
Saeed
PS. Based on my experiences, the output of CBS extrapolation for a binary complex always includes 12 sections printed out as “==> Stages <==” but the above-mentioned calculation comprises 15 of such section, while the studied complex is a binary one.
OUTPUT:
N-Body: Complex Energy (fragments = (1, 2), basis = (1, 2): -453.92286085738567)
==> N-Body: Counterpoise Corrected (CP) energies <==
n-Body Total Energy [Eh] I.E. [kcal/mol] Delta [kcal/mol]
1 -454.015163867553 0.000000000000 0.000000000000
2 -453.922663778010 58.044682513375 58.044682513375
==> N-Body: Non-Counterpoise Corrected (NoCP) energies <==
n-Body Total Energy [Eh] I.E. [kcal/mol] Delta [kcal/mol]
1 -454.015163867553 0.000000000000 0.000000000000
2 -453.922860857386 57.921013338352 57.921013338352
=> Loading Basis Set <=
Name: DEF2-SVP
Role: ORBITAL
Keyword: BASIS
atoms 1-2 entry F line 150 file /home/saeed/miniconda/share/psi4/basis/def2-svp.gbs
atoms 3 entry N line 110 file /home/saeed/miniconda/share/psi4/basis/def2-svp.gbs
atoms 4 entry C line 90 file /home/saeed/miniconda/share/psi4/basis/def2-svp.gbs
atoms 5 entry NA line 190 file /home/saeed/miniconda/share/psi4/basis/def2-svp.gbs
Psi4 stopped on: Saturday, 30 October 2021 06:39PM
Psi4 wall time for execution: 1:23:46.11
*** Psi4 exiting successfully. Buy a developer a beer!