|
|
|
Ghost atoms must be created like normal chemical elements. The ADF database does not provide the ghost database files. They are easily constructed from the normal database file of the pertaining chemical element: only the frozen core references have to be adapted such that the ghost atom will not have a frozen core. This affects the sections `CORE' and `DESCRIPTION' in the database file (see the User's Guide).
For the creation of the Carbon ghost atom with basis II the database file is:
BASIS
1S 5.40
2S 1.24
2S 1.98
2P 0.96
2P 2.20
END
CORE 0 0 0 0
END
DESCRIPTION
END
FIT
1S 10.80
2S 11.59
.... (etc.: until the end identical to the normal C database file)
END
Observe that there are four integers zero after the keyword CORE, indicating that there are no s-, p-, d-, or f-type frozen core shells. Specification of any frozen core shells would imply the insertion of (core) electrons around the ghost atoms in the calculation.
Consequently, the data block directly below CORE is empty: no Slater-type functions are required to describe any frozen core orbitals.
Finally, the DESCRIPTION data block is empty: no expansion coefficients that would describe the frozen core orbitals in terms of the Slater-type expansion functions.
All other data (apart from the title, which is just a label) in the Create data file are unchanged. The ghost file has the same Basis set, the same Fit set as for a normal atom. The values of the fit coefficients are irrelevant and could as well be put zero altogether: in the SCF part of the Create run on the ghost atom the fit coefficients will be set to zero after the first cycle since there is no charge density to be fitted.
Then the corresponding Create run is carried out.
Create Gh.C q=0 m=0 file=in.ghost
end input
eor
mv TAPE21 t21.C_ghost
The options `q=' and `m=' specify the nuclear charge and atomic mass respectively. Both are zero for a ghost atom: it is not a physical object, only the center for a set of functions.
In the same fashion the Oxygen and Chromium ghost atoms are created. The inputs for these are not shown here.
For the BSSE calculations we first do the `normal' calculations of CO and Cr(CO)5, yielding the fragment files t21.CO and t21.CrCO5. The input files for these calculations are not shown here.
For the CO BSSE calculation the standard CO must have been computed first. In the BSSE run a Cr(CO)5 ghost fragment basis set is then added to the `normal' CO input. The energy change (the printed `bond energy' in the output) is the BSSE.
The input file for the CO-BSSE run is:
atoms
Gh.Cr 0 0 0
Gh.C -1.86 0 0
Gh.C 1.86 0 0
Gh.C 0 1.86 0
Gh.C 0 -1.86 0
Gh.C 0 0 -1.86
Gh.O 3.03 0 0
Gh.O -3.03 0 0
Gh.O 0 3.03 0
Gh.O 0 -3.03 0
Gh.O 0 0 -3.03
C 0 0 1.86 f=CO
O 0 0 3.03 f=CO
end
fragments
Gh.Cr t21.Cr_ghost
Gh.C t21.C_ghost
Gh.O t21.O_ghost
CO t21.CO
end
symmetry C(4V)
integration 4
endinput
In the output we find in the Bond Energy section:
hartree |
eV |
kcal/mol |
kJ/mol | |
Pauli Repulsion |
||||
Kinetic: |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
Coulomb: |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
LDA-XC: |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
Total : |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
Steric Interaction |
||||
Pauli Repulsion: |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
Electrostatic: |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
El.static (Fit correction): |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
Total: |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
Orbital Interactions |
||||
A1 : |
-0.0018366... |
-0.0500 |
-1.15 |
-4.82 |
A2 : |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
B1 : |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
B2 : |
0.0000000000 |
0.0000 |
0.00 |
0.00 |
E1 : |
-0.0020224641 |
-0.0550 |
-1.27 |
-5.31 |
Total : |
-0.00386... |
-0.1051 |
-2.42 |
-10.14 |
Alternative Decomposition Orb.Int. |
||||
(...) |
||||
Total Bonding Energy : |
-0.00386... |
-0.1051 |
-2.42 |
-10.14 |
The BSSE for CO is computed as 2.42 kcal/mole
In similar fashion the BSSE is computed for Cr(CO)5. In the BSSE run a ghost CO is added to the normal Cr(CO)5 input:
atoms
Cr 0 0 0 f=CrCO5
C 1.86 0 0 f=CrCO5
C -1.86 0 0 f=CrCO5
C 0 1.86 0 f=CrCO5
C 0 -1.86 0 f=CrCO5
C 0 0 -1.86 f=CrCO5
O 3.03 0 0 f=CrCO5
O -3.03 0 0 f=CrCO5
O 0 3.03 0 f=CrCO5
O 0 -3.03 0 f=CrCO5
O 0 0 -3.03 f=CrCO5
Gh.C 0 0 1.86
Gh.O 0 0 3.03
end
fragments
CrCO5 t21.CrCO5
Gh.C t21.C_ghost
Gh.O t21.O_ghost
end
symmetry C(4v)
integration 4
endinput
The Bond Energy result yields 1.93 kcal/mole for the BSSE.
The bonding of CO to Cr(CO)5 is computed in the normal way (not included in the sample): from fragments CO and Cr(CO)5. The obtained value for the bond energy is then simply corrected for the two BSSE terms, 4.35 kcal/mole together.