  Based on the first-principles calculations and theoretical analysis, we
investigate the electronic structures, topological phase transition (TPT) and
topological properties of layered magnetic compound MnSb2Te4. It has the
similar crystal and magnetic structure as the magnetic topological insulator
MnBi2Te4. We find that when the spin-orbit coupling (SOC) is considered, the
band structure of MnSb2Te4 in antiferromagnetic (AFM) state has no band
inversion at {\Gamma}. This is due to the SOC strength of Sb is less than that
of Bi. The band inversion can be realized by increasing the SOC of Sb by 0.3
times, which drives MnSb2Te4 from a trivial AFM insulator to an AFM topological
insulator (TI) or axion insulator. Uniaxial compressive strain along the layer
stacking direction is another way to control the band inversion. The interlayer
distance shorten by 5% is needed to drive the similar TPT. For the
ferromagnetic (FM) MnSb2Te4 with experimental crystal structure, it is a normal
FM insulator. The band inversion can happen when SOC is enhanced by 0.1 times
or the interlayer distance is decreased by more than 1%. Thus, FM MnSb2Te4 can
be tuned to be the simplest type-I Weyl semimetal with only one pair of Weyl
nodes on the three-fold rotational axis. These two Weyl nodes are projected
onto (1-10) surface with one Fermi arc connecting them.
