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.)