Surface model for x > 10%: In the case of higher nickel concentration, the nickel clusters as shear planes along the [121] orientation in the crystal . A simple way to model this behavior is to lay out a [121] plane of height 2 Å in the unit cell, converting all ruthenium atoms within the volume to nickel. It is then possible to count LOER sites on the surface. The nickel concentration of the structure can then be controlled by the distance between any two of these planes. For the case of one nickel plane per three cells the surface saturation of nickel is 20%. It is then possible to count the number of Ru-Ni bridge sites in the surface.