Symbol	Representation
a	Lattice constant
c	Unit cell height
$c_{\mathrm{b}}$	Concentration of bulk sites
$c_{\mathrm{s}}$	Concentration of surface sites
$D_{\mathrm{H}}$	Diffusion coefficient of hydrogen
$D_{\mathrm{H}·\mathrm{H}}$	Binding energy of molecular hydrogen
$D_{\mathrm{H}·\mathrm{M}}$	Hydrogen-metal binding energy
d	Diameter
E	Activation energy
H	Enthalpy
h	Planck constant
J	Flux
K	Solubility
k	Reaction rate constant
$k_{\mathrm{B}}$	Boltzmann constant
M	Molar mass
N	Solver sample size
$N_{\mathrm{AV}}$	Avogadro constant
n	Coordination number
P	Membrane permeability
p	Pressure
$Q_{{\mathrm{H}}_2·{\mathrm{M}}_2}$	Binding energy of molecularly adsorbed hydrogen
R	Gas constant
r	Reaction rate
S	Entropy
T	Temperature
$v_g$	Atomic volume
x	Bulk concentration
${\gamma }_{\mathrm{D}}$	Structural factor for diffusion
$\delta$	Membrane thickness
$\theta$	Surface coverage
$\mathsf{\Lambda }$	Arrhenius pre-exponential factor
${\lambda }_t$	Thermal wavelength
$\rho$	Density
$\Phi$	Molar flow rate
${\chi }_{\mathrm{H}·{\mathrm{M}}_{\mathrm{s}}}$	Saturation solubility