An Interatomic Pair Potential for Aluminium Calculation of Stacking Fault Energy

Abstract

A potential function for aluminium is derived from phonon dispersion curves. The contribution from short-range multi-ion interactions is substracted from the phonon data, and this affecto markedly the short-range characteristics of the potential. The potential function is used for tho calculation of the energies of intrinsic and extrinsic stacking faults. Certain multi-ion contributions to these energies are also evaluated. The calculation cannot explain the experimentally observed difference between Vntr and yextr, which is attributed here to the interpretation of loop annealing observations in such faults. A re-interpretation gives approximntely 120 mJ/m2 for Iritroiluc tioriOur knowledge of atomic interactions has increased greatly during the last twenty years. The pair potential approach or its equivalent, the second-order pseudopotential approach, appear to be appropriate only for simple metals, and are in suspect in the case of noble or transition metals. Of the technically important metals, only a hmininni belongs to the first group, but even its treatment suffers from limitations. The selection of the pseudopotential and the screening function is not unique, and for this reason a variety of more or less fundamental pair potentials have been constructed for this metal. I n addition, those third-and higher-order terms in electron-ion interaction which contribute to pairwise atomic interaction are generally omitted from the calculations. Neither has empirical derivation yielded reliable pair potentials, for these are frequently of short range and are fitted to experiniental data by assuming the non-pairwise higher-order terms to be negligible. The pseudopotential theory indicates that the former is a poor assumption, and there is both theoretical and experimental evidence that the latter is not strictly correct in the case of Al.The objective here is t o construct a pair potential for A1 by fitting a long-range function derived from pseudopotential theory to experimental phonon frequencies.It is known that phonon dispersion curves in aluminium are not in agreement with the central force model. This is an indication of non-pairwise multi-ion forces. A large l) Oulu, Finland. 6'

Effect of alloying elements on the stacking fault energies of dilute al-based alloys

“…Table 4. By comparing with the reliable measured data, 135±20 [19] , 166 [18] , 150±40 mJm -2 [17], and the predicted values 120 [49], 122 [13], 124 [13], 134 [13], 130 [20], 142 [16], 146 [12], 158 [21], and 162 mJm -2 [22] (10)) due to the effect of alloying element X are also listed, as well as the corresponding fitting errors (err) are also listed. All quantities for volume are in Å 3…”

An analytical bond-order potential for the aluminum copper binary system

“…Once this is achieved, the positions of atoms in the crystalline half of the block (containing 6144 atoms) are fixed (atom velocities are memorized so that they can be recovered when this fixed condition is released as will be discussed below), and the temperature of the other half of the system is continuously increased employing the NPT dynamics except that only the pressure in the direction normal to the melt interface is controlled at 0 GPa whereas the lateral directions are held fixed at the size of the crystalline portion of the simulation. [62,63]. Many of literature potentials cannot capture this.…”

Prediction of Dislocation Cores in Aluminum from Density Functional Theory

“…Calculated and measured lattice constant, elastic constants (Mbar), and stacking fault energy (mJ=m 2 ) for fcc aluminum[23][24][25][26]. The VASP calculated values are based on different levels of approximation of the pseudopotentials and the local density approximation as described in the text.…”