  A new lattice Boltzmann model for multicomponent ideal gas mixtures is
presented. The model development consists of two parts. First, a new kinetic
model for Stefan- Maxwell diffusion amongst the species is proposed and
realized as a lattice Boltzmann equation on the standard discrete velocity set.
Second, a compressible lattice Boltzmann model for the momentum and energy of
the mixture is established. Both parts are consistently coupled through mixture
composition, momentum, pressure, energy and enthalpy whereby a passive scalar
advection-diffusion coupling is obviated, unlike in previous approaches. The
proposed model is realized on the standard three-dimensional lattices and is
validated with a set of benchmarks highlighting various physical aspects of
compressible mixtures. Stefan-Maxwell diffusion is tested against experiment
and theory of uphill diffusion of argon and methane in a ternary mixture with
hydrogen. The speed of sound is measured in various binary and ternary
compositions. We further validate the Stefan-Maxwell diffusion coupling with
hydrodynamics by simulating diffusion in opposed jets and the three-dimensional
Kelvin-Helmholtz instability of shear layers in a two-component mixture. Apart
from the multicomponent compressible mixture, the proposed lattice Boltzmann
model also provides an extension of the lattice Boltzmann equation to the
compressible flow regime on the standard three-dimensional lattice.
