Using the adiabatic trajectory method, the migration energy barriers for the migration of Li ions and Cr ions along the one-dimensional diffusion pathway in pure and Cr doped LiFePO4 were obtained from first principles calculations. The results showed that while Li ions could diffuse along the diffusion pathway easily, Cr ions did not easily diffuse away from their initial positions. This  meant that the heavy Cr ions would block the one-dimensional diffusion pathway of the material. Monte Carlo simulations were performed to evaluate the influences of the blocking behaviors on the electrochemical performance of LiFePO4 cathode material for Li ion secondary batteries. The results showed that the evaluated capacity was highly sensitive to the amount of the dopant, the size of the super-cell being used for simulation (particle size of the powder cathode material) and the Monte Carlo steps for statistics (charge-discharge current density.

The Effect of Cr Doping on Li Ion Diffusion in LiFePO4 from First Principles Investigations and Monte Carlo Simulations. C.Y.Ouyang, S.Q.Shi, Z.X.Wang, H.Li, X.J.Huang, L.Q.Chen: Journal of Physics Condensed Matter, 2004, 16[13], 2265-72