Calculating Quantum Transports Using Periodic Boundary Conditions
  An efficient new method is presented to calculate the quantum transports using periodic boundary conditions. This new method is based on a method we developed previously, but with an essential change in solving the Schrodinger's equation. As a result of this change, the scattering states can be solved at any given energy. Compared to the previous method, the current method is faster and numerically more stable. The total computational time of the current method is similar to a conventional ground state calculation. Details of the procedure is presented in the current paper. 
Lin-Wang Wang