  The high pressure phase diagrams of TaAs family (NbP, NbAs, TaP and TaAs) are
explored systematically using crystal structure search together with
first-principles calculations. Our calculations show that NbAs and TaAs have
similar phase diagrams and possess the same structural phase transition
sequence of I41md $\rightarrow$ P-6m2 $\rightarrow$ P21/c $\rightarrow$ Pm-3m,
with a bit different transition pressures. The phase transition sequence of NbP
and TaP are somewhat different from that of NbAs and TaAs. In which new
structures emerge, for instance, the Cmcm structure in NbP and the Pmmn
structure in TaP. It is found interestingly that in the electronic structure of
the high-pressure phase P-6m2-NbAs, there are Weyl points and triple degenerate
points coexisted, similar to the high-pressure P-6m2-TaAs.
