sample.materialdb - Materials Database

air	Empty layer (all sld = 0)
water	A solid block of material, described by its bulk density
H2O	A solid block of material, described by its bulk density
heavywater	A solid block of material, described by its bulk density
D2O	A solid block of material, described by its bulk density
lightheavywater	A solid block of material, described by its bulk density
DHO	A solid block of material, described by its bulk density
silicon	A solid block of material, described by its bulk density
Si	A solid block of material, described by its bulk density
sapphire	A solid block of material, described by its bulk density
Al2O3	A solid block of material, described by its bulk density
gold	A solid block of material, described by its bulk density
Au	A solid block of material, described by its bulk density
permalloy	A solid block of material, described by its bulk density
Ni8Fe2	A solid block of material, described by its bulk density

Common materials in reflectometry experiments along with densities.

By name:

air, water, heavywater, lightheavywater, silicon, sapphire, gold
permalloy

By formula:

H2O, D2O, DHO, Si, Al2O3, Au, Ni8Fe2

If you want to adjust the density you will need to make your own copy of these materials. For example, for permalloy:

>>> NiFe=Material(permalloy.formula, density=permalloy.bulk_density)
>>> NiFe.density.pmp(10)  # Let density vary by 10% from bulk value
Parameter(permalloy density)