  By using bare Argonne V4' (AV4'), V6' (AV6'), and V8' (AV8') nucleon-nucleon
(NN) interactions respectively, the nuclear equations of state (EOSs) for
neutron matter are calculated with the unitary correlation operator and
high-momentum pair methods. The neutron matter is described under a finite
particle number approach with magic number $N=66$ under a periodic boundary
condition. The central short-range correlation coming from the short-range
repulsion in the NN interaction is treated by the unitary correlation operator
method (UCOM) and the tensor correlation and spin-orbit effects are described
by the two-particle two-hole (2p2h) excitations of nucleon pairs, in which the
two nucleons with a large relative momentum are regarded as a high-momentum
pair (HM). With the 2p2h configurations increasing, the total energy per
particle of neutron matter is well converged under this UCOM+HM framework. By
comparing the results calculated with AV4', AV6', and AV8' NN interactions, the
effects of the short-range correlation, the tensor correlation, and the
spin-orbit coupling on the density dependence of the total energy per particle
of neutron matter are demonstrated. Moreover, the contribution of each
Hamiltonian component to the total energy per particle is discussed. The EOSs
of neutron matter calculated within the present UCOM+HM framework agree with
the calculations of six different microscopic many-body theories, especially in
agreement with the auxiliary field diffusion Monte Carlo calculations.
