PyDDM.ISF_and_DDMmatrix_theoretical_models.dTheorySingleExp_Nonerg_DDM

PyDDM.ISF_and_DDMmatrix_theoretical_models.dTheorySingleExp_Nonerg_DDM

dTheorySingleExp_Nonerg_DDM(lagtime, amplitude, tau, bg, s, C)

Theoretical model for the DDM matrix with an exponential term for the intermediate scatting function. Also contains a non-ergodicity parameter. With this, the ISF will decay to the non-ergodicity paramter (C), instead of to zero as is the case with ergodic systems.

Parameters
  • lagtime (array) – 1D array of the lagtimes

  • amplitude (float) – Amplitude, “A” in equation below

  • tau (float) – The characteristic decay time

  • bg (float) – Background term, “B” in equation below

  • s (float) – Stretching exponent

  • C (float) – The non-ergodicity parameter

Returns

ddm_matrix – DDM matrix as shown in equation below

Return type

array

Notes

\[\begin{split}f(q, \Delta t) = e^{\left( \frac{-\Delta t}{\tau}\right)^{s}} + C \\ D(q, \Delta t) = A \times (1 - f(q, \Delta t)) + B\end{split}\]

A non-ergodic model was used in the paper below. 1

References

1

Cho, J. H., Cerbino, R. & Bischofberger, I. Emergence of Multiscale Dynamics in Colloidal Gels. Phys. Rev. Lett. 124, 088005 (2020).