Comparative studies of interatomic potentials for modeling point defects in wurtzite GaN

In this paper, a new version of the Stillinger-Weber (SW) potential for wurtzite GaN is presented, by which we systematically explore the structural and thermodynamical properties of native point defects and their complexes. In parallel, the semi-empirical Modified Embedded-Atom Method (MEAM) potential is selected for comparison. The SW and MEAM potentials are assessed by the reproduction of the fundamental properties of wurtzite GaN and by the ability to describe the inversion domain boundaries and the wurtzite-rocksalt phase transition. Then the structural search of native point defects and their complexes in GaN is implemented using both SW and MEAM potentials with the benchmark of Density Functional Theory (DFT) calculations. Besides vacancies and antisites, four N and five Ga interstitials are confirmed by refining the DFT calculations, among which two N split interstitials N+ - N(2 (11) over bar0) and N+ - Ga < 01 (1) over bar0 >, and two Ga split interstitials, Ga+ - Ga(01 (1) over bar0) - g and Ga+ - N < 01 (1) over bar0 >, are observed for the first time. The SW potential correctly predicts the octahedral occupation Ga-Oct to be the most stable Ga interstitial, while the MEAM potential predicts the ground state of the N+ - N(01 (1) over bar0) split interstitial ( N+ - N < 01 (1) over bar0) - g) as the most stable N interstitial. However, neither of the two potentials could simultaneously generate the most stable configurations of N and Ga interstitials. The investigations of point defect complexes reveal that N octahedral Frenkel [Frenkel(Oct)(N)] and paired antisite (NGaGaN) defects are unstable and get converted into V-N circle plus N+ - N < 01 (1) over bar0 > - g configurations with different separations between V-N and N+ - N < 01 (1) over bar0 > - g point defects based on the DFT calculations. The formation energies calculated by the DFT and SW potential demonstrate that Schottky, Ga octahedral Frenkel [Frenkel(Oct)(Ga)], and VN circle plus N+ - N < 01 (1) over bar0 > - g point defect complexes are energetically feasible and that they should not dissociate into two isolated point defects. In contrast, the MEAM potential predicts the dissociation to be exothermic for Schottky and VN circle plus N+ - N < 01 ($1) over bar0 > - g. Overall, the structural features concerned with N-N or Ga-Ga bonds relaxed by the SW potential are more consistent with DFT calculations than the MEAM counterpart. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).