Requests for technical support from the VASP group should be posted in the VASP-forum.

Instead of the previous iteration scheme, which is just some kind of Quasi-Newton scheme, it also possible to optimize the expectation value of the Hamiltonian using a successive number of conjugate gradient steps. The first step is equal to the steepest descent step in section Single band steepest descent scheme. In all following steps the preconditioned gradient ${\displaystyle g_{n}^{N}}$ is conjugated to the previous search direction. The resulting conjugate gradient algorithm is almost as efficient as the algorithm given in Efficient single band eigenvalue-minimization. For further reading see [1][2][3].

## References

1. M.P. Teter, M.C. Payne and D.C. Allan, Phys. Rev. B 40, 12255 (1989).
2. D.M. Bylander, L. Kleinman and S. Lee, Phys Rev. B 42, 1394 (1990).
3. [ W.H. Press, B.P. Flannery, S.A. Teukolsky and W.T. Vetterling, em Numerical Recipes (Cambridge University Press, New York, 1986).]