Center for Molecular Modeling - S. De Waele

A first-principles reassessment of the Fe-N phase diagram in the low-nitrogen limit

kurt — Fri, 28 Sep 2018 08:44:28 +0000

S. De Waele, K. Lejaeghere, E. Leunis, L. Duprez, S. Cottenier

Journal of Alloys and Compounds

775, 758-768

2019

DOI

http://dx.doi.org/10.1016/j.jallcom.2018.09.356

Precipitation in simultaneously nitrided and aged Mo-containing maraging steel

waele — Mon, 19 Jun 2017 11:36:52 +0000

A. Verdiere, C. Hofer, S. De Waele, V. Bliznuk, S. Primig, S. Cottenier, M. D. Tran, B. Pennings, L. A. I. Kestens, R. H. Petrov

Materials Characterization

131, 21-30

2017

Abstract

The excellent mechanical properties of maraging steels are ascribed to nanometer-sized intermetallics which precipitate during aging in the ductile very low carbon Ni-martensite. Their wear and fatigue properties can be improved by nitriding. The non-equilibrium precipitation reactions in Fe-Ni-Co-Mo maraging steels are studied during an aging heat treatment executed in a nitriding atmosphere. The precipitates formed during the initial stages of precipitation are characterized with transmission electron microscopy and atom probe tomography. Spherical intermetallic precipitates having a diameter of around 3 nm were detected in the aged, bulk material. These ω-type precipitates formed during the early stages of aging, have a trigonal crystal lattice and their chemical composition is close to (Fe,Ni)7Mo2. In the nitrided layer, Mo-N disc-shaped nitrides on the {100} martensitic lattice having a diameter of 3 to 4 nm were found but their exact crystal structure could not be determined with microstructural characterization techniques. Density functional theory calculations confirmed that a single layer of Mo atoms, substituting Fe on the {100} plane of the Fe-matrix, is stable and showed that the N atoms prefer to be in the Mo-layer, on the octahedral sites with Fe as nearest neighbors.

DOI

http://dx.doi.org/10.1016/j.matchar.2017.06.014

Private attachment

1-s2.0-S1044580316307719-main.pdf

Error estimates for density-functional theory predictions of surface energy and work function

kurt — Sat, 24 Sep 2016 09:52:20 +0000

S. De Waele, K. Lejaeghere, M. Sluydts, S. Cottenier

Physical Review B

Vol. 94, Iss. 23 — 15 December 2016

2016

Abstract

Density-functional theory (DFT) predictions of materials properties are becoming ever more widespread. With increased use comes the demand for estimates of the accuracy of DFT results. In view of the importance of reliable surface properties, this work calculates surface energies and work functions for a large and diverse test set of crystalline solids. They are compared to experimental values by performing a linear regression, which results in a measure of the predictable and material-specific error of the theoretical result. Two of the most prevalent functionals, the local density approximation (LDA) and the Perdew-Burke-Ernzerhof parametrization of the generalized gradient approximation (PBE-GGA), are evaluated and compared. Both LDA and GGA-PBE are found to yield accurate work functions with error bars below 0.3 eV, rivaling the experimental precision. LDA also provides satisfactory estimates for the surface energy with error bars smaller than 10%, but GGA-PBE significantly underestimates the surface energy for materials with a large correlation energy.

Open Access version available at UGent repository

DOI

https://doi.org/10.1103/PhysRevB.94.235418

Private attachment

PhysRevB.94.235418.pdf

Predicting Phase Stability in Nitrogen Steels with Density-Functional Theory

samuel — Tue, 14 Jan 2020 08:01:43 +0000

S. De Waele

Tue, 17/12/2019

https://biblio.ugent.be/publication/8642676

Supervisors

Prof. Dr. Stefaan Cottenier, dr. ir. Lode Duprez, Dr. ir. Kurt Lejaeghere

Attachment (private)

De Waele.pdf

Assessing DFT reproducibility using a systematic benchmark set: Chemical variety

martin — Tue, 10 Jul 2018 12:39:37 +0000

Period

Friday, 6 July, 2018 to Friday, 15 March, 2019

Node days

2 212.00 days

Users

M. Callsen, S. De Waele, K. Lejaeghere, S. Cottenier

Remaining days

2 212.00 days

TIER1 reference n°

2018-33

Status

Approved

The Fe-Si phase diagram: from electrical steel to the planet Mercury

wim — Mon, 05 Mar 2018 13:44:23 +0000

Process-property-microstructure assessment of novel High-Entropy Alloys

wim — Mon, 05 Mar 2018 10:28:33 +0000

Developing new iron-nitrogen steels with ab initio thermodynamics

wim — Mon, 05 Mar 2018 10:21:49 +0000

Stacking silver differently for improved surface properties

wim — Mon, 05 Mar 2018 09:50:49 +0000

Error estimation in molecular dynamics simulations: nitrogen impurities in iron with machine learning potentials

wim — Mon, 05 Mar 2018 08:09:55 +0000