  We performed first-principles molecular dynamics calculations for lithium
using the projector augmented waves method and the generalized gradient
approximation as exchange-correlation energy. The melting curve of lithium was
computed using the \textit{Z}-method technique for pressures up to 30 GPa,
which agrees well with the experimental and two-phase simulated results. The
change of the melting line slope from positive to negative was predicted by the
characteristic shape inversion of the \textit{Z} curve at about 8.2 GPa.
Through analyzing the static properties, we conclude that no liquid-liquid
phase transition accompanies the occurrence of the melting line maximum, which
is caused by the higher compressibility of the liquid phase compared to the
solid phase. In addition, we systematically studied the dynamic and optical
properties of lithium near melting curve at critical superheating and melting
temperatures. It was suggested that spectra difference at critical superheating
and melting temperature may be able to diagnose the homogeneous melting.
