Material database module.

This module provides access to the material database.

The material database is a collection of material records. Each record describes a material and contains the following fields:

  • name: material name

  • type: material type, either crystal or amorphous

  • density: material density in g/cm^3

  • atoms: list of atoms in the material. Each atom is described by a dictionary with the following fields:

    • symbol: atom symbol

    • x: x coordinate of the atom in the unit cell

    • y: y coordinate of the atom in the unit cell

    • z: z coordinate of the atom in the unit cell

    • occ: occupancy of the atom in the unit cell

    • repeat: number of atoms in the unit cell

The material database is stored in a YAML file. The file contains a list of material records. The user can add new records to the database by editing a copy of the YAML material database file.

To get a copy of the material database file, use the copy_db() method.

Example:
>>> from escape.scattering.mdb import copy_db
>>> copy_db()

The copy of the material database file is stored in the current working directory.

In order to compile the new material database, the user should create an instance of the new material database using mdb() method. This method will look for the YAML material database file in the current working directory and will compile the material database from the YAML file. The compiled material database is stored in the current working directory and is used by default. If the local MDB file is not found, the method will look for the MDB file in the specific folder of the package.

escape.scattering.mdb.mdb(mdbdir=None)

Create a material database object.

Parameters:
mdbdirstr

Path to the directory with the material database file.

Returns:

Material database object.

escape.scattering.mdb.copy_db(overwrite=False)

Copy the material database file to the current working directory.

escape.scattering.mdb.neutrons(wavelength, units='angstrom', name='Neutron source')

Create a neutron source object.

Parameters:
wavelengthfloat

Wavelength of the neutron radiation.

unitsstr

Units of the wavelength, ‘angstrom’ or ‘nm’.

Returns:

Neutron source object.

escape.scattering.mdb.xrays(wavelength, units='angstrom', name='X-ray source')

Create an X-ray source object.

Parameters:
wavelengthfloat

Wavelength of the X-ray radiation.

unitsstr

Units of the wavelength, ‘angstrom’ or ‘nm’.

Returns:

X-ray source object.

class escape.scattering.mdb.mdb_obj

This object represents a material database.

ABSORPTION_WAVELENGTH = 1.798
DATADIR = 'mdb'
ELEMENTSDBFN = 'elements.db'
MATERIALSDBFN = 'materials.db'
MATERIALSYAMLFN = 'materials.yaml'
add(self, dict rec)

Add a material record to the database.

Parameters:
recdict

Material record.

amorph_density(self, unicode amorph)
amorphs

Returns list of amorphous materials names in the database. :returns:

list of strings

compile_elements_db(self, datadir, dbfn)

Compile the elements database from the data files in the given directory.

Parameters:
datadirstr

Path to the directory with the data files.

dbfnstr

Name of the elements database file.

compile_materials_db(self, datadir, mdbfn)

Compile the materials database from the data files in the given directory.

Parameters:
datadirstr

Path to the directory with the data files.

mdbfnstr

Name of the materials database file.

copy_db(type cls, overwrite=False)

Copy the material database file to the current working directory.

crystal_density(self, unicode crystal)
crystals

Returns list of crystal materials names in the database. :returns:

list of strings

load_elements_db(self, unicode dbrelpath, unicode escdir)
load_materials_db(self, unicode datadir, unicode dbfn, unicode escdir)
parse_element(self, symbol)
sf(self, unicode element, source_obj src, Q=None)
class escape.scattering.mdb.source_obj

This object represents a source of radiation.

type

Returns type of the source. :returns:

string value

units

Returns units of the source. :returns:

string value

wavelength

Returns wavelength of the source. :returns:

double value

exception escape.scattering.mdb.MdbError