Tip

All input files can be downloaded: Files.

thermo

This keyword defines the parameters for thermodynamic analysis based on frequency calculation results.

Options

temp

Value	A real number
Default	298.15

The temperature (in Kelvin) for thermodynamic analysis. The default value is 298.15 K.

pressure

Value	A real number
Default	1.

The pressure (in atm) for thermodynamic analysis. The default value is 1.0 atm.

point_group_delta

Value	A real number
Default	0.01

A threshold to determine the point group of the molecule. The default value is 0.01. The smaller point_group_delta, the more accurate the symmetry point group will be determined. However, a very small value may lead to failure in point group determination. If you encounter such problem, please increase this value gradually (e.g., to 0.1).

Theoretical Background

Input Examples

Example: XX

For the complex GeH₃F-NCH, we can do EDA calculation by the following input:

eda-1.inp

mol
   Ge      0.00000000      0.00221863     -0.79935317
    H      0.00000000      1.48645043     -0.40384625
    H      1.28514604     -0.74161126     -0.40477816
    H     -1.28514603     -0.74161126     -0.40477816
    F      0.00000000      0.00108752     -2.56116087
    C      0.00000000     -0.00225138      3.35662076
    H      0.00000000     -0.00220444      4.43604901
    N      0.00000000     -0.00207825      2.20326200
end

basis
    def2-svp
end

scf
    charge  0
    spin2p1 1
    type    U # For EDA calculations, this must be added explicitly.
end

grimmedisp
    type bj
end

eda
    type tso # You can also change it to: gks
    frag 0 1 1-5  # Define GeH3F.
    frag 0 1 6-8  # Define HCN.
end

task
    eda b3lyp
end

The atom indices are shown below:

The results are:

TSO-EDA ResultsGKS-EDA Results

eda-tso.out

WITH BSSE correction:
Electrostatic interaction energy:                  -4.98 kcal/mol
Exchange-correlation interaction energy:            4.22 kcal/mol
Polarization interaction energy:                   -0.62 kcal/mol
Charge transfer interaction energy:                -1.31 kcal/mol
Grimme's dispersion interaction:                   -1.58 kcal/mol
----------------------------------------------------------------
Total interaction energy:                          -4.27 kcal/mol

We can see that the total interaction energies (with or without BSSE) are the same for both TSO-EDA and GKS-EDA methods, but components are different. As mentioned, Qbics recommends TSO-EDA for calculations. This complex is stabilized by Electrostatic interaction eneregy, which is compatible with the chemical intuition that it is stabilized by sigma-hole.