  The origin of nonproportionality in scintillator materials has been a long
standing problem for more than four decades. In this manuscript, we show that,
with the help of first principle modeling, the parameterization of the
nonproportionality for several systems, with respect to their band structure
curvature suggests a correlation between carrier effective mass and energy
response. We attribute this correlation to the case where free electrons and
holes are the major energy carriers. Excitonic scintillators do not show such a
definitive trend. This model suggests a potential high-throughput approach for
discovering novel proportional scintillators in the former class of materials.
