# Observers¶

## ClusterExpansionObserver¶

class mchammer.observers.ClusterExpansionObserver(cluster_expansion, interval=None, tag='ClusterExpansionObserver')

This class represents a cluster expansion (CE) observer.

A CE observer allows to compute a property described by a CE along the trajectory sampled by a Monte Carlo (MC) simulation. In general this CE differs from the CE that is used to generate the trajectory. For example in a canonical MC simulation the latter would usually represent an energy (total or mixing energy) whereas the former CE(s) could map lattice constant or band gap.

Parameters: cluster_expansion (icet.ClusterExpansion cluster expansion model) – to be used for observation tag (str) – human readable observer name (default: ClusterExpansionObserver) interval (int) – observation interval during the Monte Carlo simulation
tag

str – name of observer

interval

int – observation interval

get_observable(atoms)

Returns the value of the property from a cluster expansion model for a given atomic configuration.

Parameters: atoms (Atoms) – input atomic structure. float
return_type

Data type of the observed data.

Return type: type