The network like arrangement of the solute atoms gives rise to a different

The network like arrangement of the solute atoms

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high. The network-like arrangement of the solute atoms gives rise to a different, third type of MRO. NATURE | Vol 439 | 26 January 2006 ARTICLES 423
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© 2006 Nature Publishing Group not appear to suppress the development of ordering, as the agree- ment between the calculated (at ultrahigh quenching rates) and experimental (for glasses obtained at lower cooling rates) partial RRDFs is remarkable (Fig. 2 and Supplementary Fig. S7). This shows that the pair correlations established in our calculated systems are similar to those in experimental samples, for the SRO and the MRO on the short-range side 46 examined here (the experimental data available for validation are for the range below 8 A ˚ , although in general MRO may extend up to approximately 2 nm; see Fig. 2 and Supplementary Fig. S7). We also compared the structure of the Ni 80 P 20 MG obtained at two different quench rates (see Methods) and found no obvious difference. To observe the effects of the small size of the system and the imposed periodic boundary conditions, we examined different sizes up to 2.2 nm for the edge length of the cube, and also modelled the Ni 80 P 20 glass using a large system of 4,000 atoms. In the latter case, however, classical molecular dynamics simulations 16 involving empirical or hypothetical interatomic potentials had to be used (binary mixture of Lennard-Jones particles using the modified Kob–Andersen interatomic potentials 47 ). All the results are consist- ent with what we have presented above. This suggests the particular MRO is not due to a small system under periodic boundary conditions. However, it is certainly true that one prefers slower cooling rates to allow the system to survey the energy landscape more thoroughly, attaining lower energy states through increased structural ordering. While SRO may converge fast, the degree and extent of the MRO development may be affected by the rapid computer quench in small systems (our RMC system is much larger, but the Monte Carlo procedure used in RMC also favours randomization). Therefore, the SRO and MRO we report here could be underestimates; the ordering actually present in the (more structurally relaxed) MGs should be at least as much. METHODS EXAFS data. Ni 80 P 20 foils with thicknesses of up to 10 m m were prepared using electroplating from Brenner-type baths onto Cu foils, which were etched away after deposition. X-ray diffraction (XRD), transmission-mode Ni K-edge and fluorescence-mode P K-edge EXAFS data were collected at beamline X14A and X15B, respectively, of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL). The EXAFS data were Fourier- transformed into real space after pre-edge and post-edge background sub- tractions. The first peak up to , 3.5 A ˚ in real space corresponding to the nearest-neighbour shell was inverse-Fourier-transformed back into k space.
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