  We have investigated the glassy behavior of a molecular crystal built up with
chloroadamantane molecules. For a simple model of this molecule and a rigid fcc
lattice a MD simulation was performed from which we obtained the dynamical
orientational correlators $S_{\lambda \lambda '}({\bf{q}},t)$ and the ``self''
correlators $S_{\lambda \lambda '}^{(s)}(t)$, with $\lambda = (\ell, m)$,
$\lambda' = (\ell', m')$. Our investigations are for the diagonal correlators
$\lambda = \lambda'$. Since the lattice constant decreases with decreasing
temperature which leads to an increase of the steric hindrance of the
molecules, we find a strong slowing down of the relaxation. It has a high
sensitivity on $\lambda$, $\lambda '$. For most $(\ell,m)$, there is a two-step
relaxation process, but practically not for $(\ell,m) = (2,1)$, $(3,2)$,
$(4,1)$ and $(4,3)$. Our results are consistent with the $\alpha$-relaxation
scaling laws predicted by mode coupling theory from which we deduce the glass
transition temperature $T_c^{MD} \cong 217K$. From a first principle solution
of the mode coupling equations we find $T_c^{MCT} \cong 267K$. Furthermore mode
coupling theory reproduces the absence of a two-step relaxation process for
$(\ell,m)=(2,1)$, $(3,2)$, $(4,1)$ and $(4,3)$, but underestimates the critical
nonergodicity parameters by about 50 per cent for all other $(\ell,m)$. It is
suggested that this underestimation originates from the anisotropic crystal
field which is not accounted for by mode coupling theory. Our results also
imply that phonons have no essential influence on the long time relaxation.
