Small Vacancy Clusters in Nickel

Abstract

on the occasion of his 80th birthdayThe method of molecular dynamics is used to compute binding energies of different configurations of vacancy clusters in nickel. The interatomic pair potential IS obtained according to the pseudopotential theory. It is found that in the range from divacancy to hexavacancy various atomic configurations are formed which can be considered as nuclei of dislocation loops, voids, and new crystal lattices.Die Methode der Molekulardynamik wird benutzt, um die Bindungsenergien verschiedener Konfigurationen von Leerstellenclustern in Nickel numerisch zu berechnen. Das interatomare Paarpotential wird entsprechend der Pseudopotentialtheorie erhalten. Es wird gefunden, daB im Bereich von der Doppelleerstelle bis zur Hexavakanz verschiedene atamare Konfigurationen gebildet werden, die als Keime fur Versetzungsschleifen, Hohlraume und neue Kristallgitter angesehen werden konnen.

Calculation of Vacancy Induced Properties in FCC Metals Using an Alternative Lattice Dynamical Model

“…Furthermore, the goodness of their fitted potentials in describing the lattice dynamical properties of nickel is quite doubtful as their model formulae for relating their empirical potentials to those physical quantities concerned are subject to many approximate assumptions and they have not calculated any phonon dispersion curves for nickel to make cross-check with the measured phonon frequencies. Finally, it is noted that Vasilyev et alJ- 21 ' have used the pseudopotential theory to construct the interatomic pair potential for nickel up to the sixth coordination sphere and the divacancy binding energy -Emt was calculated to be 0.066 ± 0.014 eV which is in fairly good agreement with ours using the DT schemes.…”

“…13,[16][17][18] ! Moreover, the past calculations of the vacancy induced properties in those metals by various previous researchers' [7][8][9][10][11][12][13][14][15][19][20][21] ! are sometimes found to be strikingly different in both signs and magnitudes.…”

First principles calculations of vacancy–vacancy interactions in nickel: thermal expansion effects

“…To our knowledge, most theoretical determinations of the formation and migration enthalpies of a divacancy in nickel are obtained from calculations based on various semiempirical methods such as molecular statics and dynamics calculations [20][21][22][23], the lattice statics model [24], or embedded atoms methods (EAM and MEAM) [25][26][27][28][29][30][31]. They lead to values ranging from 2.50 to 2.98 eV for H f 2v , 0.19 to 1.17 eV for H m 2v , and 0.004 to 0.44 eV for H b 2v .…”

“…Starting from the experimental data on self-diffusion by Hoffman et al [15] and by taking into account the presence of divacancies as well as the temperature dependence of energies and entropies related to the formation and migration of monovacancies, Seeger and Schumacher [13] deduced that H f 2v = 2.42 eV, H m 2v = 0.82 eV, and H b 2v = 0.28 eV. Maier et al [11] combined their self-diffusion measurements with those of [18] a , 0.33, 0.44 [19] c , 0.28 [13] c 0.066 ± 0.014 [21] e , 0.12 [28] d , 0.268 [24] d , 0.21-0.34 [29] d , 0.40 [27] d , 0.09 [30] d , 0.44 [26] d , 0.23 [22] e , 0.04 [33] f 0.004 [23] e , 0.25 [25] d 0.067 [32] g , 0.19 [20] e , [21] d H m 2v 0.99, 1.16 [18] a , 0.83, 1.12 [19] c , 0.82 ± 0.03 [13] c , 0.72 ± 0.07 [16] a 0.19 [31] d , 0.66 [27] d , 0.33, 0.63 [30] d , 0.674 [22] e , 0.90 [25] d , 1.17 [26] d , 0.96, 0.47 [20] e , 0.47 [23] e Q 2v 3.58( [18] and [19]) a,c , 4.15 ± 0.69 [2] Bakker [14] in order to cover a large temperature region (542-1400 • C). They deduced a value of Q 2v = 3.7 eV.…”