\(\renewcommand\AA{\unicode{x212B}}\)
This fitting function models the dynamics structure factor of a particle undergoing discrete jumps on N-sites evenly distributed in a circle. The particle can only jump to neighboring sites. This is the most common type of discrete rotational diffusion in a circle.
Markov model for jumps between neighboring sites:
The Decay fitting parameter \(\tau\) is the inverse of the transition rate. This, along with the circle radius \(r\), conform the two fundamental fitting parameters of the structure factor \(S(Q,E)\):
The transition rate, expressed in units of energy is \(h\tau^{-1}\), with h = 4.135665616 meV ps.
This function is a composite of ElasticDiffRotDiscreteCircle and InelasticDiffRotDiscreteCircle.
When using DiffRotDiscreteCircle, the value of Q can be obtained either though the Q attribute or can be calculated from the input workspace using the WorkspaceIndex property. The value calculated using the workspace is used whenever the Q attribute is empty.
Methyl Rotations can be modelled setting N=3. In this case, the inelastic part reduces to a single Lorentzian:
If, alternatively, one models these dynamics using the Lorentzian function provided in Mantid:
Then:
Name | Type | Default | Description |
---|---|---|---|
N | |||
NumDeriv | |||
Q | |||
f0.N | |||
f0.Q | |||
f0.WorkspaceIndex | |||
f1.N | |||
f1.Q | |||
f1.WorkspaceIndex |
\(N\) (integer, default=3) number of sites - \(NumDeriv\) (boolean, default=true) carry out numerical derivative - \(Q\) (double, default=0.5) Momentum transfer .. properties:
.. categories::
C++ header: DiffRotDiscreteCircle.h (last modified: 2021-03-31)
C++ source: DiffRotDiscreteCircle.cpp (last modified: 2021-05-10)