TY - THES

T1 - Development of a semi-automated molecular dynamics workflow for testing interatomic potentials against ab-initio data

AU - Halkali, Celine

N1 - no embargo

PY - 2022

Y1 - 2022

N2 - The experimental investigation of properties and behavior of materials has been increasingly complemented by computer-aided methods for several decades. Molecular dynamics simulations serve as a good combination of simple implementation and low computational effort with comparatively large system dimensions. Experiments on small scales tend to be cost-intensive and time-consuming. However, the knowledge of small scale processes in materials can give significant insight into bulk properties. This is also true for nickel-based superalloys, where e.g. the partitioning of species to various phases, grain boundaries and defects can lead to a considerable change in properties. The aim of this work is to test interatomic potentials fitted to experimental data with respect to their comparability with results from ab-initio methods. Interatomic potentials developed for different, nickel-based material systems were tested for their applicability to face-centered cubic elemental nickel, body-centered cubic ß-NiAl (B2), and face-centered cubic Ni¿Al (L1¿). Equilibrium lattice parameter, elastic properties, and nickel vacancy formation energy of all three phases, as well as the stacking fault, surface, and grain boundary energies of elemental nickel, were calculated and compared with results from ab-initio calculations. Depending on the properties to which the potentials were fitted, the calculated values agree well with those obtained from ab-initio simulations. The results of the respective potentials for the equilibrium lattice parameters and elastic properties are in better agreement with the experimental values, since most of the time, they are parameters of the potential curves. The same is true for the vacancy formation energies if they were used for the potential development. Most of the stacking fault energies give satisfactory results. The surface energies, while generally lower than the ab-initio simulations, follow the ¿¿¿¿ > ¿¿¿¿ > ¿¿¿¿ trend observed from these. Good results are obtained for the grain boundary energy, which was not included in the curve fitting for any of the potentials, but is still very close to the ab-initio results. Most of the tested interatomic potentials are particularly suitable for the calculation of planar defect energies as a good part of these values agree well with those of the ab-initio calculations.

AB - The experimental investigation of properties and behavior of materials has been increasingly complemented by computer-aided methods for several decades. Molecular dynamics simulations serve as a good combination of simple implementation and low computational effort with comparatively large system dimensions. Experiments on small scales tend to be cost-intensive and time-consuming. However, the knowledge of small scale processes in materials can give significant insight into bulk properties. This is also true for nickel-based superalloys, where e.g. the partitioning of species to various phases, grain boundaries and defects can lead to a considerable change in properties. The aim of this work is to test interatomic potentials fitted to experimental data with respect to their comparability with results from ab-initio methods. Interatomic potentials developed for different, nickel-based material systems were tested for their applicability to face-centered cubic elemental nickel, body-centered cubic ß-NiAl (B2), and face-centered cubic Ni¿Al (L1¿). Equilibrium lattice parameter, elastic properties, and nickel vacancy formation energy of all three phases, as well as the stacking fault, surface, and grain boundary energies of elemental nickel, were calculated and compared with results from ab-initio calculations. Depending on the properties to which the potentials were fitted, the calculated values agree well with those obtained from ab-initio simulations. The results of the respective potentials for the equilibrium lattice parameters and elastic properties are in better agreement with the experimental values, since most of the time, they are parameters of the potential curves. The same is true for the vacancy formation energies if they were used for the potential development. Most of the stacking fault energies give satisfactory results. The surface energies, while generally lower than the ab-initio simulations, follow the ¿¿¿¿ > ¿¿¿¿ > ¿¿¿¿ trend observed from these. Good results are obtained for the grain boundary energy, which was not included in the curve fitting for any of the potentials, but is still very close to the ab-initio results. Most of the tested interatomic potentials are particularly suitable for the calculation of planar defect energies as a good part of these values agree well with those of the ab-initio calculations.

KW - Molekulardynamik

KW - interatomare Potentiale

KW - Nickelbasis-Superlegierung

KW - Molecular dynamics

KW - interatomic potentials

KW - nickel-based superalloys

U2 - 10.34901/mul.pub.2023.83

DO - 10.34901/mul.pub.2023.83

M3 - Master's Thesis

ER -