  Recently, the family of rare-earth chalcohalides were proposed as candidate
compounds to realize the Kitaev spin liquid (KSL). In the present work, we
firstly propose an effective spin Hamiltonian consistents with the symmetry
group of the crystal structure. Then we apply classical Monte Carlo simulations
to preliminarily study the model and establish a phase diagram. When
approaching to the low temperature limit, several magnetic long range orders
are observed, including the stripe, the zigzag, the antiferromagnetic (AFM),
the ferromagnetic (FM), the incommensurate spiral (IS), the Multi-$\pmb {Q}$
and the 120{\deg}. We further calculate the thermodynamic properties of the
system, such as the temperature dependence of the magnetic susceptibility and
the heat capacity. The ordering transition temperatures reflected in the two
quantities agree with each other. For most interaction regions, the system is
magnetically more susceptible in the $ab$-plane than in the $c$-direction. The
stripe phase is special, where the susceptibility is fairly isotropic in the
whole temperature region. These features provide useful information to
understand the magnetic properties of related materials.
