Wigner_Seitz_radius

plasmapy.formulary.quantum.Wigner_Seitz_radius(n: Unit("1 / m3")) -> Unit("m")

Calculate the Wigner-Seitz radius, which approximates the inter- particle spacing. It is the radius of a sphere whose volume is equal to the mean volume per atom in a solid. This parameter is often used to calculate the coupling parameter. When ion density is used, this is the ion sphere radius, i.e., the space occupied by a single ion with no other ions in that space. Higher density means less space for each ion, so the radius is smaller.

Parameters:

n (Quantity) – Particle number density.

Returns:

radius – The Wigner-Seitz radius in meters.

Return type:

Quantity

Raises:

• TypeError – If argument is not a ~astropy.units.Quantity.
• UnitConversionError – If argument is in incorrect units.
• ValueError – If argument contains invalid values.

Warns:

~astropy.units.UnitsWarning – If units are not provided, SI units are assumed.

Notes

The Wigner-Seitz radius approximates the interparticle spacing. It is the radius of a sphere whose volume is equal to the mean volume per atom in a solid:

\[r = \left(\frac{3}{4 \pi n}\right)^{1/3}\]

See also

Fermi_energy()

Example

>>> from astropy import units as u
>>> Wigner_Seitz_radius(1e29 * u.m**-3)
<Quantity 1.33650462e-10 m>