  We study the global phase diagram of magnetic orders and lattice structure in
the Fe-pnictide materials at zero temperature within one unified theory, tuned
by both doping and pressure. On the low doping and high pressure side of the
phase diagram, there is one single transition, which is described by a $z=2$
mean field theory with very weak run-away flows; on the high doping and low
pressure side the transition is expected to split to two transitions, with one
O(3) spin density wave transition followed by a z = 3 quantum Ising transition
at larger doping. The fluctuation of the strain field fluctuation of the
lattice will not affect the spin density wave transition, but will likely drive
the Ising nematic transition more mean field like through a linear coupling, as
observed experimentally in BaFe_2-xCo_xAs_2.
