Material

A metatype for defining materials properties.

Attributes

Name	Type	Description
density	`number`	Material density, in kg/m³.
elements	`table`	Atomic elements composition. The table contains mass fractions indexed with atomic elements symbols.
I	`number`	Mean Excitation Energy (MEE), in GeV.
state	`string`	Material state. One of `'solid'`, `'liquid'` or `'gas'`.

a	`number`	Sternheimer $a$ coefficient (see below).
k	`number`	Sternheimer $k$ coefficient (see below).
x0	`number`	Sternheimer $x_0$ coefficient (see below).
x1	`number`	Sternheimer $x_1$ coefficient (see below).
Cbar	`number`	Sternheimer $\overline{C}$ coefficient (see below).
delta0	`number`	Sternheimer $\delta_0$ coefficient (see below).

ZoA	`number`	The ratio $Z / A$ of the charge number over the mass number (g/mol) averaged over atomic components.

Note

The ZoA attribute is informative only. Changing its value has no effect on the material properties.

Constructor

The Material constructor takes a single table argument specifying the material properties as keywords. A material is defined by its density and its atomic composition. The atomic composition can be provided by a chemical formula or as a table of mass fractions indexed with atomic elements symbols. Optionally one can also specify the material Mean Excitation Energy (I) and the material state ('solid', 'liquid' or 'gas'). If the mean excitation energy is not provided it is estimated from the atomic composition using Bragg additivity rule.

The ionization loss of charged particles depends on the material atomic spacing, i.e. on its density (see e.g. Sternheimer et al., 1984). A parameterization of this effect is provided in Sternheimer, 1952 as function of a set of cooefficients: $a$ , $k$ , $x_0$ , $x_1$ $\overline{C}$ and $\delta_0$ . If these coefficients are not explicitly defined when building the material then their values will be estimated using the material density and I following Sternheimer and Peirs, 1971.

Synopsis

pumas.Material{density=, (elements)=, (formula)=, (I)=, (state)=,
    (a)=, (k)=, (x0)=, (x1)=, (Cbar)=, (delta0)=}

Arguments

Name	Type	Description
density	`number`	Material density, in kg/m³.

elements	`table`	Atomic elements composition. The table contains mass fractions indexed with atomic elements symbols.
formula	`string`	Chemical formula, e.g. `'H2O'`.

I	`number`	Mean Excitation Energy (MEE), in GeV.
state	`string`	Material state. One of `'solid'`, `'liquid'` or `'gas'`.

a	`number`	Sternheimer $a$ coefficient (see above).
k	`number`	Sternheimer $k$ coefficient (see above).
x0	`number`	Sternheimer $x_0$ coefficient (see above).
x1	`number`	Sternheimer $x_1$ coefficient (see above).
Cbar	`number`	Sternheimer $\overline{C}$ coefficient (see above).
delta0	`number`	Sternheimer $\delta_0$ coefficient (see above).