Electric and Magnetic Fields

Electric Field

The external electric field is handled at the AMS level, see the documentation there.

The effect of a magnetic filed can be approximated by the following potential: \(\mu_B \vec{\sigma}_i \vec{B}\), where \(\mu_B\) is the Bohr magneton, \(\vec{\sigma}_i\) are the Pauli matrices and \(\vec{B}\) is the magnetic field. For Spin-unrestricted collinear calculations, the spin is assumed to be aligned with the z-axis.

Magnetic Field

BField
   Bx float
   By float
   Bz float
   Dipole Yes/No
   DipoleAtom integer
   Method [NR_SDOTB | NR_LDOTB | NR_SDOTB_LDOTB]
   Unit [tesla | a.u.]
End
BField
Type:Block
Description:The effect of a magnetic filed can be approximated by the following potential: mu * sigma_i * B, where mu is the Bohr magneton, sigma_i are the Pauli matrices and B is the magnetic field
Bx
Type:Float
Default value:0.0
Unit:Tesla
Description:Value of the x component of the BField
By
Type:Float
Default value:0.0
Unit:Tesla
Description:Value of the y component of the BField
Bz
Type:Float
Default value:0.0
Unit:Tesla
Description:Value of the z component of the BField
Dipole
Type:Bool
Default value:No
GUI name:Bfield is: Atomic dipole
Description:Use an atomic dipole as magnetic field instead of a uniform magnetic field.
DipoleAtom
Type:Integer
Default value:1
GUI name:on atom number
Description:Atom on which the magnetic dipole should be centered (if using the dipole option)
Method
Type:Multiple Choice
Default value:NR_SDOTB
Options:[NR_SDOTB, NR_LDOTB, NR_SDOTB_LDOTB]
Description:There are two terms coupling to an external magnetic field. One is the intrinsic spin of the electron, called S-dot-B, the other one is the orbital momentum call L-dot-B. The L.B is implemented non-relativistically, using GIAOs in the case of a homogeneous magnetic field (not for the dipole case).
Unit
Type:Multiple Choice
Default value:tesla
Options:[tesla, a.u.]
Description:Unit of magnetic filed. The a.u. is the SI version of a.u.

Atom-wise fuzzy potential

FuzzyPotential # Non-standard block. See details.
   ...
End
FuzzyPotential
Type:Non-standard block
Description:Atomic (fuzzy cell) based, external, electric potential. See example.

Example:

FuzzyPotential
   scale $scale
   a1 v1   ! atom with index a1 gets potential coefficient v1 (a.u.)
   a2 v2   ! atom a2 gets potential v2
   ...
End
scale

Overall scaling factor to be applied.

If an atom is not in the list it gets a coefficient of zero. The potential of an atom is its number (\(v_i\)) as specified on input times its fuzzy cell

\[V(r) = \sum_i^\text{atoms} v_i \mathcal{P}_{i,U} (r)\]

using the same partition function \(\mathcal{P}\) as for the BeckeGrid. A partition function (or fuzzy cell) of an atom is close to one in the neighborhood of this atom.

The sign convention is: negative is favorable for electrons. (Unit: a.u.)