12. Spin-Orbit DFT (SODFT)

The spin-orbit DFT module (SODFT) in the NWChem code allows for the variational treatment of the one-electron spin-orbit operator within the DFT framework. The implementation requires the definition of an effective core potential (ECP) and a matching spin-orbit potential (SO). The current implementation does NOT use symmetry.

The actual SODFT calculation will be performed when the input module encounters the TASK directive (Section 5.10).

  TASK SODFT

Input parameters are the same as for the DFT, see section 11 for specifications. Some of the DFT options are not available in the SODFT. These are max_ovl and sic.

Besides using the standard ECP and basis sets, see Section 8 for details, one also has to specify a spin-orbit (SO) potential. The input specification for the SO potential can be found in section 8.2. At this time we have not included any spin-orbit potentials in the basis set library.

Note: One should use a combination of ECP and SO potentials that were designed for the same size core, i.e. don't use a small core ECP potential with a large core SO potential (it will produce erroneous results).

The following is an example of a calculation of $\mathrm{UO_2}$:

start uo2_sodft
echo

Memory 32 mw

charge 2

geometry noautoz noautosym units angstrom
 U     0.00000      0.00000     0.00000
 O     0.00000      0.00000     1.68000
 O     0.00000      0.00000    -1.68000
end

basis "ao basis" cartesian print
U    S
        12.12525300         0.02192100
         7.16154500        -0.22516000
         4.77483600         0.56029900
         2.01169300        -1.07120900
U    S
         0.58685200         1.00000000
U    S
         0.27911500         1.00000000
U    S
         0.06337200         1.00000000
U    S
         0.02561100         1.00000000
U    P
        17.25477000         0.00139800
         7.73535600        -0.03334600
         5.15587800         0.11057800
         2.24167000        -0.31726800
U    P
         0.58185800         1.00000000
U    P
         0.26790800         1.00000000
U    P
         0.08344200         1.00000000
U    P
         0.03213000         1.00000000
U    D
         4.84107000         0.00573100
         2.16016200        -0.05723600
         0.57563000         0.23882800
U    D
         0.27813600         1.00000000
U    D
         0.12487900         1.00000000
U    D
         0.05154800         1.00000000
U    F
         2.43644100         0.35501100
         1.14468200         0.40084600
         0.52969300         0.30467900
U    F
         0.24059600         1.00000000
U    F
         0.10186700         1.00000000
O    S
        47.10551800        -0.01440800
         5.91134600         0.12956800
         0.97648300        -0.56311800
O    S
         0.29607000         1.00000000
O    P
        16.69221900         0.04485600
         3.90070200         0.22261300
         1.07825300         0.50018800
O    P
         0.28418900         1.00000000
O    P
         0.07020000         1.00000000
END

ECP
U nelec 78
  U s
    2          4.06365300        112.92010300
    2          1.88399500         15.64750000
    2          0.88656700         -3.68997100
  U p
    2          3.98618100        118.75801600
    2          2.00016000         15.07722800
    2          0.96084100          0.55672000
  U d
    2          4.14797200         60.85589200
    2          2.23456300         29.28004700
    2          0.91369500          4.99802900
  U f
    2          3.99893800         49.92403500
    2          1.99884000        -24.67404200
    2          0.99564100          1.38948000
O nelec 2
  O s
    2         10.44567000         50.77106900
  O p
    2         18.04517400         -4.90355100
  O d
    2          8.16479800         -3.31212400
END

SO
  U p
  2    3.986181      1.816350
  2    2.000160     11.543940
  2    0.960841      0.794644
  U d
  2    4.147972      0.353683
  2    2.234563      3.499282
  2    0.913695      0.514635
  U f
  2    3.998938      4.744214
  2    1.998840     -5.211731
  2    0.995641      1.867860
END

dft
  mult 1
  xc hfexch
  odft
  grid fine
  convergence energy 1.000000E-06
  convergence density 1.000000E-05
  convergence gradient 1E-05
  iterations 100
  mulliken
end

task sodft