  An efficient first principles method was developed to calculate spin transfer
torques in layered system with noncollinear magnetization. The complete
scattering wave function is determined by matching the wave function in the
scattering region with the Bloch states in the leads. The spin transfer torques
are obtained with aid of the scattering wave function. We applied our method to
the ferromagnetic spin valve and found that the material (Co, Ni and Ni80Fe20)
dependence of the spin transfer torques could be well understood by the Fermi
surface. Ni has much longer spin injection penetration length than Co.
Interfacial disorder is also considered. It is found that the spin transfer
torques could be enhanced by the interfacial disorder in some system.
