Example: B3LYP: H2PO

Download H2PO_B3LYP.run

Example shows an unrestricted B3LYP calculation. In this case ADF also calculates the hyperfine interactions at H, P, and O nuclei (keyword ESR).

The ‘DEPENDENCY’ key is set to 1e-4. Note that for hybrids and Hartree-Fock the dependency key is always set. The default value in that case is 4e-3. By explicitly setting the ‘DEPENDENCY’ key we can use a lower value, which is possible in this case. One should check that the results remain reliable if one uses a smaller value for the ‘DEPENDENCY’ key.

$ADFBIN/adf << eor
Title hfs H2PO B3LYP TZ2P
Atoms
    O   1.492  0.000  0.000
    P   0.000  0.000  0.000
    H  -0.600 -0.650  1.100
    H  -0.600 -0.650 -1.100
End
xc
 hybrid B3LYP
end
Basis
 Type TZ2P
 Core None
End
dependency bas=1e-4
BeckeGrid
 Quality good
End
ZlmFit
 Quality good
End
esr
end
unrestricted
charge 0 1
end input
eor

For the hyperfine interactions it is important to use all-electron basis sets on the interesting nuclei. One can get more accurate results if one uses a larger basis set, like the QZ4P basis set, which is present in the $ADFRESOURCES/ZORA directory. The Basis key should then be:

Basis
 Type ZORA/QZ4P
 Core None
End

The QZ4P results for the isotropic value of the A-tensor are approximately: -24.61 MHz for ¹⁷ O, 957.33 MHz for ³¹ P, and 110.83 MHz for ¹ H.

You may want to compare the results with previous B3LYP results by N. R. Brinkmann and I. Carmichael, J. Phys. Chem. A (2004), 108, 9390-9399, which give for the Isotropic Fermi Contact Couplings (MHz) for the ² A’ State of H₂ PO using B3LYP, with an aug-cc-pCVQZ basis set: -24.24 MHz for ¹⁷ O, 963.33 MHz for ³¹ P, and 111.51 MHz for ¹ H.