a	Amount adsorbed at saturation (mol kg−1)
b	Langmuir constant (Pa−1)
B	Mobility as defined by Equation (11)
C	Concentration (mol m−3)
D	Diffusivity (m2 s−1)
E	Activation energy (kJ mol−1)
J	Permeation flux (mol m−2 s−1 Pa−1)
kb	Force constant for bond-stretching (kJ mol−1 m−2)
k θ	Force constant for angle-bending (kJ mol−1 rad−2)
L	Thickness (m)
M	Molecular mass (g mol−1)
p	Partial pressure (Pa)
Q	Partial atomic charge (e)
q	Amount of adsorbed (mol kg−1)
r	Distance (m)
R	Gas constant (=8.314 J K−1 mol−1)
T	Temperature (K)
V	Diffusion volume (cm3)
Symbols
Γ	Thermodynamic factor defined by Equation (14)
δ	Kronecker delta (dimensionless)
ε	Porosity (dimensionless)
ε 0	Vacuum permittivity (=8.85 × 10−12 F m−1)
Φ	Interaction potential energy (kJ mol−1)
ϕ	Depth of potential (kJ mol−1)
θ	Binding angle (rad)
Θ	Surface coverage (dimensionless)
ρ	Density of zeolite (kg m−3)
σ	Distance at zero-potential energy (m)