Basic example of specular reflectometry simulation with BornAgain.
The sample consists of 20 alternating Ti and Ni layers.
"""importbornagainasbafrombornagainimportdeg,angstromdefget_sample():# Define materialsm_ambient=ba.MaterialBySLD("Vacuum",0,0)m_ti=ba.MaterialBySLD("Ti",-1.9493e-06,0)m_ni=ba.MaterialBySLD("Ni",9.4245e-06,0)m_substrate=ba.MaterialBySLD("SiSubstrate",2.0704e-06,0)# Define layersambient_layer=ba.Layer(m_ambient)ti_layer=ba.Layer(m_ti,30*angstrom)ni_layer=ba.Layer(m_ni,70*angstrom)substrate_layer=ba.Layer(m_substrate)# Define samplesample=ba.MultiLayer()sample.addLayer(ambient_layer)foriinrange(10):sample.addLayer(ti_layer)sample.addLayer(ni_layer)sample.addLayer(substrate_layer)returnsampledefget_simulation(sample,scan_size=500):simulation=ba.SpecularSimulation()scan=ba.AngularSpecScan(1.54*angstrom,scan_size,0,2*deg)simulation.setScan(scan)simulation.setSample(sample)returnsimulationif__name__=='__main__':importba_plotsample=get_sample()simulation=get_simulation(sample)ba_plot.run_and_plot(simulation)
makes the script executable under Unix-like operating systems,
see the chapter on how to run scripts
from the command line.
Lines between triple quotes
Text, text, text
imports the Python module bornagain (small caps, see chapter on
how to find BornAgain),
and assigns it the alias ba for brevity.
Classes and functions from the BornAgain API are
now available with the prefix ba..
makes a few frequently used symbols, namely the unit multipliers for
degree and angstrom, available without prefix.
get_sample is a function without arguments.
It returns an object of type MultiLayer.
The return statement is preceded by three stances.
Each stance starts with a comment line,
# comment extends from hash character to end of line
BornAgain functions that start with a capital letter,
like MaterialBySLD or Layer are constructors or
constructor-like global functions.
They return new objects. An object is an instance of a class.
The function MaterialBySLD instantiates an object of type
the function Layer an object of type
Function like addLayer is a member function of class
This can be seen from the two lines
where sample is created as a new instance of class MultiLayer.
get_simulation(sample, scan_size=500) is a function with one
required argument (sample) and one optional keyword argument
(scan_size). If the function is called with only one argument,
then scan_size is assigned the default value 500.
angstrom and deg are numeric constants. They are used to
convert physical quantities to internal units nanometer and radian.
is standard Python idiom.
It ensures that the following is executed if and only if this script
is executed directly, as a main program,
but not if this script is included as a submodule in some other code.
call the two functions defined above
in order to obtain the sample model
and then the full simulation setup, comprising sample and instrument model.
Finally, the single line
runs the simulation and plots the result, using MatPlotLib.
It uses the module
imported a few lines before.
See section Plot and export
for other ways of running simulations and plotting or exporting results.