In ALMO EDA, a system is divided into two or more molecular
fragments. The occupied molecular orbitals (MOs) on a
fragment are constructed from only the atomic orbitals of the
same fragment,31,32 as opposed to conventional MOs that are
delocalized over the entire system. The constructed MOs that are
localized on fragments are called absolutely localized molecular
orbitals (ALMOs). Such a localization constraint enables decomposition
of the overall binding energy between fragments into the
following terms:
ΔE ¼ ΔEGD þ ΔEFRZ þ ΔEPOL þ ΔECT þ ΔEHO
ð2Þ
The geometry distortion (GD) term is the energy penalty required
to distort the isolated fragments from their equilibrium geometries
into the geometries they have in the complex. The frozen
density (FRZ) term is the energy change resulting from bringing
the infinitely separated distorted fragments into the complex
geometry without any relaxation of the MOs on the fragments
(apart from readjustments to satisfy the Pauli principle). The
FRZ term constitutes a combination of Coulomb and exchange-
correlation interactions. The polarization (POL) term
accounts for the energetic stabilization due to the intramolecular
relaxation of each fragment’s absolutely localized MOs in the
presence of the other fragment(s). The charge-transfer (CT) term
is the difference between the energy obtained with the relaxed
ALMOs (i.e., after polarization has been allowed) and that from
the self-consistent (SCF) calculation with fully delocalized MOs.
The CT term includes the energy lowering due to electron
transfer from occupied orbitals on one fragment to virtual
orbitals of another fragment and further energy change induced
by the occupied-virtual mixing. The occupied-virtual mixing term
can be decomposed further into forward and backward components
through a perturbative single Roothaan step correction.48
Induction effects accompanying occupied-virtual charge transfer
are included in the higher order (HO) term and are generally
small.31 Lastly, the bondings between fragments are represented
in terms of just a few localized orbitals called significant
COVPs.32 The visualization of significant COVPs for adsorbed
CO and H2S is presented in the following section. ALMO EDA
calculations were performed with QChem 3.249 with B3LYP
functional on the Gaussian-optimized geometries of the adsorption
complexes. The same ECP basis set was used for transition
metals, and the 6-311++G(2d,p) basis set was used for all other
atoms. Basis set superposition error (BSSE) corrections evaluated
by the counterpoise method50 were taken into account.
In ALMO EDA, a system is divided into two or more molecular
fragments. The occupied molecular orbitals (MOs) on a
fragment are constructed from only the atomic orbitals of the
same fragment,31,32 as opposed to conventional MOs that are
delocalized over the entire system. The constructed MOs that are
localized on fragments are called absolutely localized molecular
orbitals (ALMOs). Such a localization constraint enables decomposition
of the overall binding energy between fragments into the
following terms:
ΔE ¼ ΔEGD þ ΔEFRZ þ ΔEPOL þ ΔECT þ ΔEHO
ð2Þ
The geometry distortion (GD) term is the energy penalty required
to distort the isolated fragments from their equilibrium geometries
into the geometries they have in the complex. The frozen
density (FRZ) term is the energy change resulting from bringing
the infinitely separated distorted fragments into the complex
geometry without any relaxation of the MOs on the fragments
(apart from readjustments to satisfy the Pauli principle). The
FRZ term constitutes a combination of Coulomb and exchange-
correlation interactions. The polarization (POL) term
accounts for the energetic stabilization due to the intramolecular
relaxation of each fragment’s absolutely localized MOs in the
presence of the other fragment(s). The charge-transfer (CT) term
is the difference between the energy obtained with the relaxed
ALMOs (i.e., after polarization has been allowed) and that from
the self-consistent (SCF) calculation with fully delocalized MOs.
The CT term includes the energy lowering due to electron
transfer from occupied orbitals on one fragment to virtual
orbitals of another fragment and further energy change induced
by the occupied-virtual mixing. The occupied-virtual mixing term
can be decomposed further into forward and backward components
through a perturbative single Roothaan step correction.48
Induction effects accompanying occupied-virtual charge transfer
are included in the higher order (HO) term and are generally
small.31 Lastly, the bondings between fragments are represented
in terms of just a few localized orbitals called significant
COVPs.32 The visualization of significant COVPs for adsorbed
CO and H2S is presented in the following section. ALMO EDA
calculations were performed with QChem 3.249 with B3LYP
functional on the Gaussian-optimized geometries of the adsorption
complexes. The same ECP basis set was used for transition
metals, and the 6-311++G(2d,p) basis set was used for all other
atoms. Basis set superposition error (BSSE) corrections evaluated
by the counterpoise method50 were taken into account.
การแปล กรุณารอสักครู่..
