SplitInterstitial

class SplitInterstitial(interstitial_element, site_element, site_index, unit_cell_index=None, cartesian_coordinates=None, fractional_coordinates=None)

Data structure for a split interstitial (dumbbell) defect. This class only holds information and does not check for physical validity, which is imposed by SplitInterstitialList during dumbbell generation. The two sets of cartesian_coordinates (or fractional_coordinates) are symmetric with respect to site_index.

Parameters:
  • interstitial_element (PeriodicTableElement) – The element to add at the given positions.
  • site_element (PeriodicTableElement) – The lattice site displaced by the an interstitial element.
  • site_index (int) – The index of the atom in the bulk unit cell configuration to be substituted with a split interstitial defect.
    Default: 0
  • unit_cell_index (sequence on int (size 3)) – The index of the unit cell in the infinite crystal which the reference site belogs to. substituted with a split interstitial defect.
    Default: (0, 0, 0)
  • cartesian_coordinates (PhysicalQuantity of type length (size 2x3) | None) – Positions at which to insert two atoms of the split interstitial defect, given in absolute coordinates. This option is mutually exclusive to fractional_coordinates.
    Default: None
  • fractional_coordinates (numpy.array (size 2x3) | None) – Positions at which to insert two atoms of the split interstitial defect, given in fractional coordinates of the bulk unit cell. This option is mutually exclusive to cartesian_coordinates.
    Default: None
cartesianCoordinates()
Returns:The coordinates of the split interstitial defect as Cartesian coordinates if they have been specified, otherwise returns None.
Return type:PhysicalQuantity of type length (size 2x3) | None
defectList()
Returns:The list of constituent defects.
Return type:list of [Vacancy | Substitutional | Interstitial]
element()
Returns:The interstitial element used in the split-interstitial defect.
Return type:int
fractionalCoordinates()
Returns:The coordinates of the split interstitial defect as fractional coordinates if they have been specified, otherwise returns None.
Return type:numpy.array (size 2x3) | None
siteIndex()
Returns:Index of the site being replaced by a split interstitial defect
Return type:int

Notes

A split interstitial is a type of defect occurring in solids. It is created by introducing an impurity interstitial_element that displaces an atom of the lattice. The pair of impurity and displaced atom is commonly referred to as a dumbbell for its resemblance to the weight-lifting device, as seen in Fig. 138.

../../../_images/arsenic_dumbbell.png

Fig. 138 Split-interstitial on GaAs. One As atom of the crystal is replaced with two atoms of the same species. This dumbbell defect is centered at the site of the original atom.