Reference.Classes.Main

Main classes in the Matlab/Octave version of WavePacket

Being based on previous Fortran versions, most of the code of the Matlab/Octave version of WavePacket project was originally written in a traditional (i.e. procedural, function-oriented) style. In the course of the years 2017/8 there was a major re-write using object-oriented programming techniques leading to version 6.0, based on the concepts of polymorphism, encapsulation and inheritance. With the introduction of the main classes listed below, it has become possible to perform fully classical, mixed quantum-classical and fully quantum mechanical simulations, both for closed and open systems, on an equal footing. In particular, by introducing the WavePacket main classes, the function qm_propa has been made polymorph, i. e., being able to propagate quantum, classical, etc. objects alike.

• class wave: Wavefunctions in position/momentum space, represented on grids
• class ket and rho: Quantum state vectors and density matrices in eigen representation
• class traj: Classical densities in phase space, represented by swarms of trajectories
• class mssh and fssh and sssh: Variants of surface hopping trajectories

The inheritance scheme of the WavePacket main classes is illustrated in the following figure

For use with the propagation function qm_propa (and partly also the other WavePacket main functions), all of the above class definitions have to provide the following methods. (In future releases, to be made mandatory by using Matlab/Octave concept of abstract classes?)

method	explanation	related variables
adiabatic	Transform forth and back between diabatic and adiabatic representation	hamilt.coupling
apply_ham	Apply Hamiltonian to the respective type of object	hamilt
init_ham	Initialize Hamiltonian for use with the respective type of object	hamilt
init_obj	Provide initial state of a propagation	time.dof and time.corr
propagate	Perform numerical propagation of a state	time
observe	Calculate expectation values of various observables of interest	expect
save/load	Save/load the propagated objects for each timestep
save_0/load_0	Save/load additional information, e.g. the Hamiltonian, expectation values etc.

In addition, all of the above class definitions have to provide the following properties, concerning saving and loading of propagated objects, i.e. wavefunctions or trajectory bundles etc. These properties are defined in the superclass generic.

property	explanation	default
save_export	If this is set to true, the propagated objects will be saved	false
save_dir	Directory where to store the propagated objects	pwd
save_file	File name template for the stored objects. Metadata is stored in file_0.mat, while the objects themselves are stored in file_1.dat, file_2.dat etc.	Class of object, i.e. 'wave', 'traj', ...
save_suffix	File name suffix for the stored objects. To be used in the context of dimension reduction with qm_balance and qm_truncate and qm_H2model	empty
save_step	Start a new file for saving objects every step main time steps. This overrides the setting of save_mem if set.	empty
save_mem	Start a new file for saving objects as soon as mem bytes have been filled. Larger files may offer slightly higher speed, but consume more memory (The saved objects are cached in memory before written to the file in one go)	500 Megabytes