Figure 8. An example snippet to run the HEOM-based absorption line shapes calculations within a Jupyter notebook.
First, the HEOM dynamics is computed to propagate the reduced density matrix of the system using the familiar function “compute.run_dynamics”. In this example, we execute the calculations twice – for two different temperatures. Note how the second call of the function takes the parameters dictionary with only two relevant parameters changed – “temperature” and “prefix”. The latter would ensure that we store the results of these two calculations in separate directories. Once the RDM evolution is computed and the results are stored in the output HDF5 file, the data can be read and used to compute the transition dipole moment ACF, Eq. 15. This is illustrated in the snippet in Figure 9a. In particular, note how Eq. 15 is implemented in a single line, thanks to object-oriented design and suitable operator overloads of the CMATRIX data class within the core of Libra package. The ACFs for two considered temperatures are illustrated in Figure 9b.