Procedure for the application of safeguard measures
Procedure for the second phase
Procedure for the generation of disordered samples In this section we describe how we generate nanosized disordered samples, relax them to find (meta)stable structures and then calculate their magnetic properties. We calculate electronic and magnetic structures within the DFT [22, 23] by means of the SIESTA code, which implements DFT on a localized basis set [24–26]. We used the LDA with the Ceperley and Alder parametrization (LDA-CA) [27, 28] and a standard built-in double-ζ polarized (DZP) [29] basis set to perform geometry relaxation. For some cases we used also the generalized gradient approximation with the Xxxxxx–Xxxxx–Ernzerhof exchange model (GGA-PBE) [30]. In general, the GGA gives much more accurate results for cohesive energy, equilibrium structure and related characteristics of molecules and crystals (table 1). Neither the LDA nor the GGA, however, can take into account the van der Waals interactions which are crucially important to describe the interlayer binding in graphite. As a result, the GGA without van der Waals interaction cannot describe the stability of graphite [31], whereas, by chance, due to error cancellation, the LDA gives a relatively accurate interlayer distance and binding energy in graphite. Therefore, it is now common practice to use the LDA for the calculation of multilayer graphitic systems (see e.g. [32] and references therein). The price to pay for this choice is that diamond becomes slightly more energetically favourable than graphite (see figure 2), contrary to experiments. We believe that this shortcoming is not important for our results.
