Anisotropic Mineral Class

class burnman.classes.anisotropicmineral.AnisotropicMineral(isotropic_mineral, cell_parameters, anisotropic_parameters, frame_convention=None, psi_function=None, orthotropic=None)

Bases: Mineral, AnisotropicMaterial

A class implementing the anisotropic mineral equation of state described in [Myh22]. This class is derived from both Mineral and AnisotropicMaterial, and inherits most of the methods from these classes.

Instantiation of an AnisotropicMineral takes three required arguments; a reference Mineral (i.e. a standard isotropic mineral which provides volume as a function of pressure and temperature), cell_parameters, which give the lengths of the molar cell vectors and the angles between them (see cell_parameters_to_vectors()), and an anisotropic parameters object, which should be either a 4D array of anisotropic parameters or a dictionary of parameters which describe the anisotropic behaviour of the mineral. For a description of the physical meaning of the parameters in the 4D array, please refer to the code or to the original paper.

For non-orthotropic materials, the argument frame_convention should be set to define the orientation of the reference frame relative to the crystallographic axes (see cell_parameters_to_vectors()).

If the user chooses to define their parameters as a dictionary, they must also provide a function to the psi_function argument that describes how to compute the tensors Psi, dPsidf and dPsidPth (in Voigt form). The function arguments should be f, Pth and params, in that order. The output variables Psi, dPsidf and dPsidth must be returned in that order in a tuple. The user should also explicitly state whether the material is orthotropic or not by supplying a boolean to the orthotropic argument.

States of the mineral can only be queried after setting the pressure and temperature using set_state().

This class is available as burnman.AnisotropicMineral.

All the material parameters are expected to be in plain SI units. This means that the elastic moduli should be in Pascals and NOT Gigapascals. Additionally, the cell parameters should be in m/(mol formula unit) and not in unit cell lengths. To convert unit cell lengths given in Angstrom to molar cell parameters you should multiply by 10^(-10) * (N_a / Z)^1/3, where N_a is Avogadro’s number and Z is the number of formula units per unit cell. You can look up Z in many places, including www.mindat.org.

Finally, it is assumed that the unit cell of the anisotropic material is aligned in a particular way relative to the coordinate axes (the anisotropic_parameters are defined relative to the coordinate axes). The crystallographic a-axis is assumed to be parallel to the first spatial coordinate axis, and the crystallographic b-axis is assumed to be perpendicular to the third spatial coordinate axis.