Abstract:For almost a century, since Bernal's attempts at a molecular theory of liquid structure (Bernal, 1937), correlation functions have been the bridge to compare theoretical calculations with experimental measurements in the study of disordered materials.Pair Distribution Functions (g(r)), Radial Distribution Functions (J(r)), Plane Angle Distributions (g(θ)) and Coordination Numbers (n c ) have been widely used to characterize amorphous and liquid materials (
“…The first procedure was by direct counting of bonded atoms, which is not trivial in metallic materials like palladium‐rich PdSi. The Bond Calculation option included in the Materials Studio Visualizer, and also implemented in the Correlation software, [ 25 ] was used. Two atoms are considered bonded if the distance between them is less than the sum of the covalent radii of the corresponding atoms times the bond parameter; in this work, a bond parameter of 1.2 was used.…”
Since the pioneering efforts of Duwez and co-workers in 1965, when a solid amorphous phase of palladium-silicon (a-PdSi) was obtained in the vicinity of the eutectic concentration, much work has been done. However, some points related to the atomic structures remain to be systematized. In this work, 8 amorphous Pd 100-c Si c alloys (c = 2.5, 5, 10, 13.34, 15, 17.5, 20, and 22 at%) are generated by molecular dynamics ab initio simulations; the short-range structure is analyzed using several correlation functions, like Pair Distribution Functions, reduced Pair Distribution Functions, Plane Angle Distribution Functions. Other related properties, like nearest-neighbors and some Frank-Kasper polyhedra are reported. The generated samples correctly reproduce the scarce experimental pair correlation functions that are reported in the literature. An unexpected outcome is the appearance of structural changes in the neighborhood of Pd 86.66 Si 13.34.
“…The first procedure was by direct counting of bonded atoms, which is not trivial in metallic materials like palladium‐rich PdSi. The Bond Calculation option included in the Materials Studio Visualizer, and also implemented in the Correlation software, [ 25 ] was used. Two atoms are considered bonded if the distance between them is less than the sum of the covalent radii of the corresponding atoms times the bond parameter; in this work, a bond parameter of 1.2 was used.…”
Since the pioneering efforts of Duwez and co-workers in 1965, when a solid amorphous phase of palladium-silicon (a-PdSi) was obtained in the vicinity of the eutectic concentration, much work has been done. However, some points related to the atomic structures remain to be systematized. In this work, 8 amorphous Pd 100-c Si c alloys (c = 2.5, 5, 10, 13.34, 15, 17.5, 20, and 22 at%) are generated by molecular dynamics ab initio simulations; the short-range structure is analyzed using several correlation functions, like Pair Distribution Functions, reduced Pair Distribution Functions, Plane Angle Distribution Functions. Other related properties, like nearest-neighbors and some Frank-Kasper polyhedra are reported. The generated samples correctly reproduce the scarce experimental pair correlation functions that are reported in the literature. An unexpected outcome is the appearance of structural changes in the neighborhood of Pd 86.66 Si 13.34.
“…The bimodal character of the second peak, typical of amorphous Pd, gradually disappears as the silicon concentration increases. The tPDFs were calculated using Correlation, an open-source software developed by Rodríguez et al 31 . Figure 3 Comparison of the Pd-Pd pPDF for the Pd Si sample with the partial experimental result of Masumoto (in Waseda’s book 27 ) 26 .…”
Section: Resultsmentioning
confidence: 99%
“…The bimodal character of the second peak, typical of amorphous Pd, gradually disappears as the silicon concentration increases. The tPDFs were calculated using Correlation, an open-source software developed by Rodríguez et al 31 .…”
In 1965 Duwez et al. reported having generated an amorphous, stable phase of palladium-silicon in the region 15 to 23 atomic percent, at.%, silicon. These pioneering efforts have led to the development of solid materials that are now known as Bulk Metallic Glasses, BMG. In 2019 Rodríguez et al. discovered, computationally, that bulk amorphous Pd becomes magnetic, and so does porous/amorphous Pd. Puzzled by these results, the study of several solid binary systems in the Pd-rich zone was undertaken; in particular, the study of the glassy metallic alloy a-Pd$$_{100-c}$$
100
-
c
Si$$_{c}$$
c
, for $$0 \le c \le 22$$
0
≤
c
≤
22
, (c in at.%) to see what their topology is, what their electronic properties are and to inquire about their magnetism. In this work it is shown that this metallic glass is in fact magnetic in the region $$0 \le c < 15$$
0
≤
c
<
15
. Collaterally $$\alpha$$
α
and $$\beta$$
β
magnetization curves are shown where the net magnetic moment is presented. The topology and the position of the first few peaks of the pair distribution functions, which agrees well with experiment, are also discussed. The BMGs produced experimentally so far are limited in size, but despite this limitation, recent industrial efforts have developed some useful devices that may revolutionize technology.
“…We analyzed the topology of the resulting structures using Correlation, a software developed by our workgroup [19], and obtained their electronic and magnetic properties after both the MD and the GO runs.…”
Magnetism is a very relevant subject that permeates our everyday lives. However, magnetism keeps taking us from surprise to surprise which seems to indicate that it is a phenomenon not well understood. For example, we found that bulk amorphous palladium becomes magnetic; so, naturally one should ask, could defective palladium develop magnetism? In particular, would amorphous porous palladium become magnetic? Here we show that the answer to that question is affirmative, this defective topology of Pd is magnetic, with a magnetism that depends on the amount of sample porosity and on the topology of their structures. Clearly, if magnetism exists in porous amorphous palladium, this indicates the possibility of developing light-weight magnets, useful when a maximized magnetism/weight ratio is demanded, well suited for space and aeronautical applications.
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