Defining a property =================== Most - if not all - H transport properties are thermally activated. Meaning they follow the Arrhenius law: :math:`X = X_0 \ \exp{\left( \frac{-E_X}{k_B \ T} \right)}` Here, :math:`X_0` is called the pre-exponential factor and :math:`E_X` is the activation energy. :math:`T` is the temperature and :math:`k_B` is the Boltzman constant. The Arrhenius law is sometimes written as: :math:`X = X_0 \ \exp{\left( \frac{-E_X}{R_g \ T} \right)}` with :math:`R_g` the gas constant. Note, :math:`R_g` and :math:`k_B` are linked by Avogadro's number :math:`N_A`. :math:`R_g = N_A \ k_B` Arrhenius parameters -------------------- Properties can be defined in HTM by using the :class:`ArrheniusProperty() ` class. .. testcode:: from h_transport_materials import ArrheniusProperty my_property = ArrheniusProperty(pre_exp=1, act_energy=0.2) More precise classes can also be used like :class:`Diffusivity() `, :class:`Solubility() `, :class:`Permeability() `, :class:`RecombinationCoeff() `, :class:`DissociationCoeff() `. .. testcode:: from h_transport_materials import Diffusivity, Solubility, Permeability my_diff = Diffusivity(D_0=1, E_D=0.2) my_sol = Solubility(S_0=1, E_S=0.2, law="henry") my_perm = Permeability(pre_exp=1, act_energy=0.2, law="sievert") Note, :class:`Solubility() ` has a `units` argument because depending on the material, the units can be m-3 Pa-1/2 (Sievert's law of solubility) or m-3 Pa-1 (Henry's law of solubility). Temperature range ----------------- A temperature range can be associated with a property. .. testcode:: from h_transport_materials import ArrheniusProperty my_property = ArrheniusProperty(pre_exp=1, act_energy=0.2, range=(300, 400)) In this example, the property is defined over the 300-400 K temperature range (see :ref:`user_units` for more information on units). Property from experimental data ------------------------------- It is possible to define an :class:`ArrheniusProperty() ` directly from (T,y) points. In this case, the Arrhenius parameters will be fitted automatically from the data points. .. testcode:: from h_transport_materials import ArrheniusProperty my_property = ArrheniusProperty( data_T=[400, 500, 600, 700], data_y=[200, 300, 400, 500] ) print(my_property) .. testoutput:: :options: +NORMALIZE_WHITESPACE Author: Material: Year: None Isotope: None Pre-exponential factor: 1.67×10³ Activation energy: 7.34×10⁻² eV/particle Attach a material ----------------- A material can be attached to a property. The simple case is to give the material as a string: .. testcode:: from h_transport_materials import ArrheniusProperty my_property = ArrheniusProperty( pre_exp=1, act_energy=0.2, material="tungsten" ) If the material already exists in the material database, the HTM object can be used instead: .. testcode:: from h_transport_materials import ArrheniusProperty, TUNGSTEN my_property = ArrheniusProperty( pre_exp=1, act_energy=0.2, material=TUNGSTEN ) .. _user_units: Units ----- HTM uses pint to automatically converts units. If no units are given, defaults units are assumed. The units are stored in a :class:`pint.UnitRegistry` that can be accessed by ``h_transport_materials.ureg``. .. testcode:: from h_transport_materials import Diffusivity, ureg my_property = Diffusivity( D_0=1 * ureg.cm**2 * ureg.s**-1, E_D=20 * ureg.kJ * ureg.mol**-1, ) print(my_property.pre_exp) print(my_property.act_energy) .. testoutput:: 0.0001 meter ** 2 / second 0.20728539312524347 electron_volt / particle This is extremely useful when units start getting complicated: .. testcode:: from h_transport_materials import Permeability, ureg my_perm = Permeability( pre_exp=1 * ureg.mol * ureg.cm**-1 * ureg.hour**-1 * ureg.bar**-0.5, act_energy=20 * ureg.kcal * ureg.mol**-1, ) print(my_perm.pre_exp) print(my_perm.act_energy) .. testoutput:: 5.289911442149285e+19 particle / meter / pascal ** 0.5 / second 0.8672820848360187 electron_volt / particle Most attributes of properties in HTM are :class:`pint.Quantity` objects: pre-exponential factors, activation energies, temperature range. Visit the `pint documentation `_ to learn more. Evaluate property at a given temperature ---------------------------------------- It is possible to evaluate the value of a property at a given temperature. .. testcode:: from h_transport_materials import Diffusivity, ureg D = Diffusivity( D_0=1 * ureg.cm**2 * ureg.s**-1, E_D=20 * ureg.kJ * ureg.mol**-1, ) print(D.value(400 * ureg.K)) .. testoutput:: 2.4446573022139513e-07 meter ** 2 / second To visualise the temperature dependency of an Arrhenius property, see :ref:`plotting_user`. Add a reference --------------- References are very important in order to track the origin of the property. Three methods exist to add a reference to a property in HTM. **Method 1:** Fields like ``author``, ``year``, and ``source`` can be added manually: .. testcode:: import h_transport_materials as htm D = htm.Diffusivity( D_0=1, E_D=0.2, author="Shrek", year=2023, source="name of book" ) **Method 2:** One can provide a source in the Bib format. .. testcode:: import h_transport_materials as htm bibsource = """@article{my_shrek_reference, title = {Name of Book}, doi = {10.1016/awesome.journal.2023.1234}, journal = {An Awesome Journal}, author = {Shrek}, year = {2023}, pages = {1--2}, }""" D = htm.Diffusivity( D_0=1, E_D=0.2, source=bibsource ) print(D.author) print(D.year) print(D.doi) .. testoutput:: shrek 2023 10.1016/awesome.journal.2023.1234 **Method 3:** In the ``h_transport_materials`` directory, there is a ``references.bib`` file containing a most of the references of HTM. One can also append the source in the Bib format to ``references.bib`` and then add the reference to ``source``. The previous example would then be: .. testcode:: import h_transport_materials as htm D = htm.Diffusivity( D_0=1, E_D=0.2, source="my_shrek_reference" ) Add notes --------- Sometimes it is useful to add custom notes to a property. .. testcode:: import h_transport_materials as htm D = htm.Diffusivity( D_0=1, E_D=0.2, note="this was measured under atmospheric pressure", )