  We present the first self-consistently computed results on the evolution of
X-ray properties of galaxy clusters in a Cold + Hot Dark Matter (CHDM) model.
We have performed a hydrodynamic plus N-body simulation for the COBE-compatible
CHDM model with standard mass components: Omega(hot) = 0.3, Omega(cold) = 0.6
and Omega(baryon) = 0.1 (h = 0.5). In contrast with the CDM model, which fails
to reproduce the observed temperature distribution function dN/dT (Bryan et al.
1994b), the CHDM model fits the observational dN/dT quite well. Our results on
X-ray luminosity are less firm but even more intriguing. We find that the
resulting X-ray luminosity functions at redshifts z = 0.0, 0.2, 0.4, 0.7 are
well fit by observations, where they overlap. The fact that both temperatures
and luminosities provide a reasonable fit to the available observational data
indicates that, unless we are missing some essential physics, there is neither
room nor need for a large fraction of gas in rich clusters: 10% (or less) in
baryons is sufficient to explain their X-ray properties. We also see a tight
correlation between X-ray luminosity and gas temperature.
