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28 TIF3: ESR PROPERTIES

Sample directory: adf/e_ESR_TiF3/

You calculate Electron Spin Resonance properties with the keywords ESR and QTENS. ESR is a block-type key and is used to compute the G-tensor or the Nuclear Magnetic Dipole Hyperfine interaction. QTENS is a simple key and invokes the computation of the Nuclear Electric Quadrupole Hyperfine interaction.

Proper usage of the key ESR requires that you do either

(a) A Spin-Orbit calculation, spin-restricted, with exactly one unpaired electron, or
(b) No Spin-Orbit terms and spin-unrestricted.

In case (a) you obtain the G-tensor. In case (b) you get the Magnetic Dipole Hyperfine interaction.

Note: in case (a) the program also prints a Magnetic Dipole Hyperfine interaction data, but these have then been computed without the terms from the spin-density at the nucleus.

After the preliminary calculations (DIRAC, to get the relativistic TAPE12 file with relativistic potentials, and the Create runs), we first calculate the Dipole Hyperfine interaction: a spin-unrestricted calculation without Spin-Orbit coupling.

Then, for the same molecule, we compute the G-tensor in a Spin-Orbit run (spin-restricted).

The here-computed and printed Dipole Hyperfine interaction misses the terms from the spin-density at the nucleus: compare with the outcomes from the first calculation.

In each of the calculations, the QTENS key invokes the computation of the Electric Quadrupole Hyperfine interaction.

Note that an all-electron calculation is carried out. This is relevant for the computation of the A-tensor, the nuclear magnetic dipole hyperfine interaction, where an accurate value of the spin-polarization density at the nucleus is important. For the G-tensor (and also for the Q-tensor) this plays a minor role, but for reasons of consistency both calculations use the same basis set and (absence of) frozen core.

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