This work is supported the Computational Materials Sciences Program funded by the US Department of Energy, Office of Science, Basic Energy Sciences, under Award Number DE-SC0020145. First-principles calculations were carried out partially on the resources of NERSC supported by the Office of Science of the US Department of Energy under contract No. DE-AC02-05CH11231, and partially on the resources of Extreme Science and Engineering Discovery Environment (XSEDE) supported by NSF with Grant No. ACI-1053575.