The reaction rate for a bulk species of index k, being added to the bulk due to surface reactions is defined as Rb,k (SI unit: mol/(s·m2)).

The reaction rate in mass basis, rb,k (SI unit: kg/(s·m2)) for species k, is given by:

with Mk (SI unit: kg/mol) being the molar mass of the species.

Based on this, the species contribution to the bulk growth velocity, vk (SI unit: m/s), is given by:

where ρk is the species density (SI unit: kg/m3).

The bulk concentration, cb,k (SI unit: mol/m2), for species k is governed by the equation:

The bulk concentration in mass basis, mb,k (SI unit: kg/m2) for a species k, can be derived from:

leading to the bulk thickness sb,k (SI unit: m) of species k according to:

The deposited total mass, mb,tot (SI unit: kg/m2) is

and the total bulk thickness, stot (SI unit: m) is