  Type Ia supernovae (SNe Ia) span a range of luminosities and timescales, from
rapidly evolving subluminous to slowly evolving overluminous subtypes. Previous
theoretical work has, for the most part, been unable to match the entire
breadth of observed SNe Ia with one progenitor scenario. Here, for the first
time, we apply non-local thermodynamic equilibrium radiative transfer
calculations to a range of accurate explosion models of sub-Chandrasekhar-mass
white dwarf detonations. The resulting photometry and spectra are in excellent
agreement with the range of observed non-peculiar SNe Ia through 15 d after the
time of B-band maximum, yielding one of the first examples of a quantitative
match to the entire Phillips (1993) relation. The intermediate-mass element
velocities inferred from theoretical spectra at maximum light for the more
massive white dwarf explosions are higher than those of bright observed SNe Ia,
but these and other discrepancies likely stem from the one-dimensional nature
of our explosion models and will be improved upon by future non-local
thermodynamic equilibrium radiation transport calculations of multi-dimensional
sub-Chandrasekhar-mass white dwarf detonations.
