The geometry found at this concentration already deviates from the current approach. This could be achieved by shifting any of the sodium atoms by half a unit cell parallel to their Adding more sodium into the system, the sodium configuration in the lowest energy structure for Na 0.75 FeHCF does not exhibit any noticeable long-range patterns. The structure of Na 1 FeHCF equals the structure that is achieved by minimizing sodium-sodium interactions.