  We extend to three-dimensional space the approximate M_2 model for the slab
geometry studied in our previous paper. The B_2 model therein, as a special
case of the second order extended quadrature method of moments (EQMOM), is
proved to be globally hyperbolic. The model we proposed here extends EQMOM to
multiple dimensions following the idea to approximate the maximum entropy
closure for the slab geometry case. Like the M_2 closure, the ansatz of the new
model has the capacity to capture both isotropic and beam-like solutions, while
the new model has fluxes in closed-form, thus is applicable to practical
numerical simulations. The rotational invariance, realizability, and
hyperbolicity of the model are studied.
