Material

A material is defined by its element composition and density. It also holds information on the material specific parameters influencing nuclear resonant scattering: The Lamb-Moessbauer factor, the abundance of the isotope and the hyperfine parameters.

The following parameters are Var objects and can be fit:

density of the material

abundance of the resonant isotope in the material

Lamb-Moessbauer factor of the resonant isotope in the material

For pure electronic calculations, only the composition and density have to be specified.

Density

The density is given in g/cm^3.

Composition

The composition is given as a list of lists that define the element symbol as a string and the relative atomic weight or atomic composition.

import nexus as nx

mat_iron_oxide = nx.Material(id = "my material",
                             composition = [["Fe", 2], ["O", 3]],
                             density = 5.3)

print(mat_iron_oxide)

Material
  .id: my material
  .composition:  Fe 2.0  O 3.0
  .density (g/cm^3) Var.value = 5.3, .min = 0.0, .max = 23.0, .fit: False, .id:
  .isotope: none
  .abundance Var.value = 0.0, .min = 0.0, .max = 1.0, .fit: False, .id:
  .lamb_moessbauer Var.value = 0.0, .min = 0.0, .max = 1.0, .fit: False, .id:
    derived parameters:
    .total_number_density (1/m^3) = 9.99372085016313e+28
    .average_mole_mass (g/mole) = 31.937400000000004
    .isotope_number_density (1/m^3) = 0.0
    number of hyperfine sites 0

When the composition of an alloy is given in wt% instead of at%, you have to convert the composition. Use the WtToAt() function from the conversions module for that

permalloy_wt = (["Ni", 80], ["Fe", 20]) # or (['Ni', 0.8], ['Fe', 0.2])

permalloy_at = nx.conversions.WtToAt([["Ni", 80], ["Fe", 20]])

print(permalloy_at)

The output is (['Ni', 0.7919215353166942], ['Fe', 0.20807846468330582])`. Similarly for Fe2O3

# Fe2O3 in relative atomic fraction
Fe2O3_at = (['Fe', 2], ['O', 3])  # or (['Fe', 0.4], ['O', 0.6])

Fe2O3_wt = nx.conversions.AtToWt(Fe2O3_at)

print(Fe2O3_wt)

to get (['Fe', 0.6994307614270416], ['O', 0.3005692385729583]).

Material Library

A material can also be loaded from the lib.material library, see material. It hosts a lot of pre-defined materials. To do so, use the materials Template method.

mat_iron_oxide = nx.Material.Template(nx.lib.material.Fe2O3)

Isotope parameters

In case nuclear scattering is calculated also the isotope properties have to be given. Those are

The abundance of the resonant isotope. The element must be in the composition of the material.

The material’s Lamb Moessbauer factor

Hyperfine parameters that specify the hyperfine interactions

mat = nx.Material(
    id = "my material",
    composition = [["Fe", 2],["O", 3]],
    density = 5.3,
    isotope = nx.lib.moessbauer.Fe57,  # load isotope from library
    abundance = 0.95,                  # "Fe" in composition is made out of 95% of 57-Fe,
    lamb_moessbauer = 0.793,
    #hyperfine_sites = [])             # list Hyperfine objects acting on the isotope

print(mat)

Here, no hyperfine parameters are passed. In this case, nuclear resonant scattering is not accounted for.

New in version 1.1.2.

The Lamb-Moessbauer factor of the material overrides the site specific Lamb-Moessabuer factors of a Hyperfine site. In case you want to use hyperfine specific Lamb_Moessbauer factors set this parameter to None.

Hyperfine interactions

Let’s define a set of hyperfine interactions, called a site,

# If no values are passed, there is no isomer shift,
# no magnetic field and no quadrupole splitting.
# It will results in an unsplit line
site = nx.Hyperfine()

# apply to the material
mat.hyperfine_sites = [site]

print(mat)

That’s it. The MoessbauerIsotope and the Hyperfine classes are covered in the next sections.

Notebooks

material - nb_material.ipynb.

Please have a look to the API Reference for more information.