Thermodynamical properties and defect energetics of an n-body potential adapted to Cu3Au

Abstract

By using molecular statics, molecular dynamics, and Monte Carlo techniques we validate a previously developed empirical n-body potential adapted to Cu3Au. At T = 0 K, predicted cohesive energies, lattice parameters, and elastic constants in CuAu and CuAu3 as well as the formation energy of vacancies in Cu3Au are in good agreement with experimental data. A satisfactory behavior is also obtained at T ~ 0 K in Cu3Au, for atomic mean-square displacements and elastic moduli. However, this model underestimates the vacancy migration energy and the order-disorder critical temperature when the latter is evaluated by Monte Carlo including both exchanges between atoms of different species and atomic moves simulating vibrations.

Second-moment interatomic potential for Cu-Au alloys based on total-energy calculations and its application to molecular-dynamics simulations

“…The phonon spectra of both ordered alloys contain several modes denoting the strong interactions between Cu and Au and they are very different compared with those of pure metals [27]. Comparing our phonon spectra with those calculated from the data of [24], we observe a reasonable agreement for the cutoff frequency and most modes, except for a shift of 0.5 THz toward lower frequencies in the centre of the spectrum for Cu 3 Au and higher frequencies in the right part of spectrum for Au 3 Cu. These differences could be resolved by direct comparison with the measured phonon DOS which are not available.…”

“…The phonon densities of states for the two L1 2 alloys are shown in figures 4(a) and 4(b) at room temperature. In these plots we present our phonon frequency spectra for comparison using the parameters of table 2 (solid lines), along with the corresponding spectra using the parameters of [24] (filled circles), which have been deduced from fitting to Solid lines refer to our MD results using the parameters of table 2; filled circles correspond to MD results using those of [24]. experimental quantities.…”

“…In the expression (1), N is the number of the particles, r ij is the distance between atoms i and j of the species α and β respectively (α, β stand for Cu or Au) and the sums over j are extended up to fifth neighbours. Usually r αβ 0 is taken equal to the first-neighbour distance in the pure systems (α ≡ β) and the alloys (a = β) [17,[22][23][24][25][26]. In the present case r αβ 0 is taken to be three additional free parameters, which with the other 12 adjustable parameters A αβ , ξ αβ , p αβ and q αβ describe the interactions in the pure elements and in the stoichiometric alloys.…”

“…Recently, the above approach has been applied to some binary cubic alloys of technological interest, such as Ni 3 Al [17] and Cu 3 Au [17,[22][23][24][25][26], aiming to describe their basic thermodynamical and structural properties. In these studies the parameters for the interactions between like atoms in the alloy have been assumed to be the same as in the respective pure metals.…”

Combined high-resolution electron microscopy and computer modeling of a ?=5 (210) [001] tilt boundary in AuCu3

“…This model has been recently developed and extensively tested by comparing computed thermodynamical properties with experimental results [13,14]. It is worth noting that the critical temperature value in AuCuz is among physical properties that have been used in fitting the potential parameters.…”