Sample

Definition of a sample, corresponding to a multilayer. A multilayer a series of horizontal layers deposited on a substrate. A multilayer may also have no layer and simply be considered as a substrate. The substrate composition, and the composition, thickness and mass thickness of each layer are defined by the Sample class.

stratagemtools.sample.CONC_UNKNOWN = None

Flag when the composition of an element is unknown.

stratagemtools.sample.CONC_DIFF = '?'

Flag when the composition of an element should be calculated by difference.

stratagemtools.sample.composition_from_formula(formula)

Calculates the composition (expressed in weight fractions) of a chemical formula.

Example:

>>> composition_from_formula('Al2O3')
... {8: 0.4707492883573059, 13: 0.5292507116426941}
Parameters:formula (str) – a valid chemical formula
Returns:composition (expressed in weight fractions). The keys of the dict are atomic numbers and the values, weight fractions.
Return type:dict
class stratagemtools.sample.Layer(composition, thickness_m=None, mass_thickness_kg_m2=None, density_kg_m3=None)

Object to store a layer definition. Once created a layer object is immutable.

Note

Should not be used directly, but via the Sample‘s methods add_layer and get_layer.

is_composition_known()

Returns whether the composition is known, i.e. contains no CONC_UNKNOWN or CONC_DIFF flag.

Return type:bool
is_thickness_known()

Returns whether the thickness is known.

Return type:bool
is_density_known()

Returns whether the density is known.

Return type:bool
composition

Returns a copy of the composition dict. The composition, and any other parameters, cannot be modified.

Returns:composition (expressed in weight fractions). The keys of the dict are atomic numbers and the values, weight fractions.
Return type:dict
thickness_m

Returns thickness in meters. It can be None if not defined.

Return type:float
mass_thickness_kg_m2

Returns mass thickness in kg/m2. It can be None if not defined.

Return type:float
density_kg_m3

Returns density in kg/m3. It can be None if not defined.

Return type:float
class stratagemtools.sample.Sample(composition, density_kg_m3=None)

Object to store a multilayer sample definition.

Parameters:
  • composition (dict) – composition of the substrate as dict where the keys are atomic numbers and the values, weight fractions. If the weight fraction is not known, set it to CONC_UNKNOWN, if the weight fraction should be calculated by difference, set it to CONC_DIFF.
  • density_kg_m3 (float) –

    mass density in kilograms per cubic meter (optional). If the composition is known, the density will be automatically calculated based on:

    \[\frac{1}{\rho} = \sum \frac{w_i}{\rho_i}\]

    where \(w_i\) and \(\rho_i\) are respectively the weight fraction and mass density of element \(i\).
add_layer(composition, thickness_m=None, mass_thickness_kg_m2=None, density_kg_m3=None)

Adds a layer below the previously added layer, or if no layer was added on top of the substrate.

Parameters:
  • composition (dict) – composition of the layer as dict where the keys are atomic numbers and the values, weight fractions. If the weight fraction is not known, set it to CONC_UNKNOWN, if the weight fraction should be calculated by difference, set it to CONC_DIFF.
  • thickness_m (float) – thickness of the layer in meters (optional). If the mass_thickness_kg_m2 and density_kg_m3 are known, the thickness will be automatically calculated.
  • mass_thickness_kg_m2 (float) – mass thickness of the layer in kilograms per square meter (optional). The mass thickness is defined as the thickness times the density. If thickness_m and density_kg_m3 are known the mass thickness will be automatically calculated.
  • density_kg_m3 (float) –

    mass density in kilograms per cubic meter (optional). If the composition is known, the density will be automatically calculated based on:

    \[\frac{1}{\rho} = \sum \frac{w_i}{\rho_i}\]

    where \(w_i\) and \(\rho_i\) are respectively the weight fraction and mass density of element \(i\).
Returns:

a layer
Return type:

Layer
pop_layer(index)

Removes the layer at index.

Parameters:index (int) – index of the layer to be removed
get_layer(index)

Returns the layer at index. Index 0 is the first layer of the multilayer, while index -1 is the last layer, the first one above the substrate.

Parameters:index (int) – index of the layer
Returns:a layer
Return type:Layer
composition

Returns the a copy of the composition of the substrate. The composition, and any other parameters, cannot be modified.

Returns:composition (expressed in weight fractions). The keys of the dict are atomic numbers and the values, weight fractions.
Return type:dict
substrate

Returns the “layer” of the substrate, a Layer object corresponding to the composition and density of the substrate.

Return type:Layer
layers

Returns a copy of layers of this sample. It cannot be modified. The layers are ordered from top to bottom.

Return type:tuple