Keywords for XEDA

All keywords are case-insensitive.

$CTR section

This group specifies the type of wavefunction, basis set and density functional theory.

METHOD=option

Computational method used in the calculation. Available methods are:

  • RHF: Restricted Hartree-Fock

  • UHF: Unrestricted Hartree-Fock

  • ROHF: Restricted Open-shell Hartree-Fock

Note

Basically, the same method will be used for both supermolecules and each monomer. For example, if METHOD=UHF is specified, UHF computations will be proceeded for both supermolecule and each monomer.

Specially, if the supermolecule is singlet while some monomers are open-shell molecules/fragments, METHOD=RHF will make the program run RHF computation for supermolecule but ROHF for monomers.

This keyword is essential even DFT is specified. See the DFT keyword for details.

BASIS=option

Specify the basis set for the computation. Currently supported basis set are listed below.

Pople’s basis sets (with * for polarization functions and + for diffusion functions):

  • 3-21G

  • 6-31G

  • 6-311G

Dunning-type correction consistent basis sets (with prefix aug- for diffusion functions):

  • cc-pVDZ

  • cc-pVTZ

  • cc-pVQZ

def2 basis sets

  • def2-SVP

  • def2-SVPP

  • def2-TZVP

  • def2-TZVPP

  • def2-QZVP

  • def2-QZVPP

  • def2-QZVPD

CHARGE=n

Total charge of the supermolecule. Default is 0, meaning the neutral molecule or radical.

NMUL=n

Spin multiplicity of the supermolecule, 1 for singlet, 2 for doublet and so on. Default is 1.

DFT

The name of density functional (M06-2X, B3LYP(-D3/-D3BJ), cam-B3LYP, PBE0, PBE, BLYP, \(\omega\)B97X-D).

Supported functionals in XEDA.

Keyword

Functional

BLYP

BLYP

B3LYP

B3LYP

B3LYP-D3

B3LYP with D3 dispersion correction

B3LYP-D3BJ

B3LYP with D3BJ dispersion correction

CAM-B3LYP

CAM-B3LYP

PBE

PBE

PBE0

Hybrid PBE with 25% HF exchange

M06-2X

M06-2X

wB97XD

\(\omega\)B97X-D

Note

If this keyword is absent, HF method will be used by default.

The DFT keyword is only used to specify the functional. Keyword METHOD=option should also be specified.

MAX_ITER=n

Maximum number of iterations. Default value is 50.

$GEO section

This group shows molecular cartesian coordinates. Only Cartesian format is supported so far. An example for water molecule is given below:

$GEO
O    0.452988940 -0.000000000 -0.000009816
H   -0.126498394  0.000000000  0.748296646
H   -0.126490546  0.000000000 -0.748286838
$END

$EDA section

This group defines the information of each monomer during EDA calculations. Currently up to 10 monomers can be supported.

Note

In this section, each line should contain only one keyword.

NMOL=n

Number of monomers.

MATOM=list

A list giving the number of atoms in each monomer. The ordering of atoms in $GEO section should be the same as the ordering of monomers. The sum of the MATOM list must be equal to the total number in the supermolecule. Numbers should be seperated by space.

MMULT=list

A list giving the multiplicity of each monomer. A positive integer means alpha spin, a negative integer means beta spin. Numbers should be seperated by space.

Tip

The summation of MMULT should be equal to the total multiplicity specified in NMUL=n. For example, if an ethane molecule is separated into two neutral CH3 groups, MMULT should be specified as MMULT=2 -2 or MMULT=-2 2.

MCHARGE=list

A list giving the charge of each monomer. The sum of the charges in the monomers must be equal to the total charge of the supermolecule as specified in CHARGE=n. Numbers should be seperated by space.

METHOD=algorithm

Algorithms used for EDA evaluation. Available options are:

  • EXACT: Coulumb and exchange terms are computed directly. (default).

  • FAST: Coulumb and exchange terms are computed with RIJ-COSK algorithm.

Note

METHOD=FAST is faster for large system with huge basis sets. For pure functional (such as PBE and BLYP), METHOD=FAST is highly recommended.

$VEC section

For the system that is difficult to converge, it is helpful to provide appropriate initial guess. The initial guess of supermolecule is given by $VEC0, and $VEC1, $VEC2, … for monomers with no BSSE correction.

Note

We can use the orbitals from one functional as the initial guess to other functional.

Bibliography

LMOEDA

  1. Su, P.; Li, H. Energy Decomposition Analysis of Covalent Bonds and Intermolecular Interactions. The Journal of Chemical Physics 2009, 131 (1), 014102.

GKSEDA

  1. Su, P.; Jiang, Z.; Chen, Z.; Wu, W. Energy Decomposition Scheme Based on the Generalized Kohn–Sham Scheme. The Journal of Physical Chemistry A 2014, 118 (13), 2531–2542.

  2. Su, P.; Tang, Z.; Wu, W. Generalized Kohn-Sham Energy Decomposition Analysis and Its Applications. WIREs Computational Molecular Science 2020, 10 (5), 1460.

  3. Tang, Z.; Song, Y.; Zhang, S.; Wang, W.; Xu, Y.; Wu, D.; Wu, W.; Su, P. XEDA, a Fast and Multipurpose Energy Decomposition Analysis Program. Journal of Computational Chemistry 2021, 42 (32), 2341–2351.