Lattice¶
The purpose of this document is to explain how Mantid is using information about unit cells and their orientation with respect to the laboratory frame. For a detailed description, see the UB matrix implementation notes.
Theory¶
The physics of a system studied by neutron scattering is described by the conservation of energy and momentum. In the laboratory frame:
Note that the left side in the above equations refer to what is happening to the lattice, not to the neutron.
Let’s assume that we have a periodic lattice, described by lattice
parameters
For such a lattice, the physics will be described in terms of reciprocal lattice parameters by
The
The
The
The
Other useful equations:
The distance in reciprocal space to the
The distance in real space to the
The angle between
Unit cells¶
The UnitCell
class provides the functions to access direct and
reciprocal lattices.
Oriented lattices¶
All the functions defined for UnitCell
are inherited by the
OrientedLattice
objects. In addition, functions for manipulating
the
Note about orientation¶
Most of the instruments have incident beam along the
Category: Concepts