Danny Vanpoucke

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Jan 09 2025

The impact of strain on the GeV-color center in diamond

Authors: Thijs G.I. van Wijk, E. Aylin Melan, Rani Mary Joy, Emerick Y. Guillaume, Paulius Pobedinskas, Ken Haenen, and Danny E.P. Vanpoucke
Journal: Carbon 234, 119928 (2025)
doi: 10.1016/j.carbon.2024.119928
IF(2024): 10.5
export: bibtex
pdf: <Carbon>

 

Graphical abstract strained GeV0.
Graphical Abstract: Schematic representation of the impact of hydrostatic and linear strain on the Zero Phonon Line of the neutral GeV defect in diamond.

Abstract

Color centers in diamond, such as the GeV center, are promising candidates for quantum-based applications. Here, we investigate the impact of strain on the zero-phonon line (ZPL) position of GeV0. Both hydrostatic and linear strain are modeled using density functional theory for GeV0concentrations of 1.61 % down to 0.10 %. We present qualitative and quantitative differences between the two strain types: for hydrostatic tensile and compressive strain, red- and blue-shifted ZPL positions are expected, respectively, with a linear relation between the ZPL shift and the experienced stress. By calculating the ZPL shift for varying GeV0 concentrations, a shift of 0.15 nm/GPa (0.38 meV/GPa) is obtained at experimentally relevant concentrations using a hybrid functional. In contrast, only red-shifted ZPL are found for tensile and compressive linear strain along the ⟨100⟩ direction. The calculated ZPL shift exceeds that of hydrostatic strain by at least one order of magnitude, with a significant difference between tensile and compressive strains: 3.2 and 4.8 nm/GPa (8.1 and 11.7 meV/GPa), respectively. In addition, a peak broadening is expected
due to the lifted degeneracy of the GeV0 eg state, calculated to be about 6 meV/GPa. These calculated results are placed in perspective with experimental observations, showing values of ZPL shifts and splittings of comparable magnitude.

Permanent link to this article: https://dannyvanpoucke.be/2025-paper-strainedgev-en/

Jan 03 2025

New QuATOMs group member: Minh-Thu Bui

Since the first of January 2025, the QuATOMs group has been strengthened with a new member: Minh-Thu Bui.

She is an expert in polymer chemistry, with a MSc in Polymers for advanced Technologies from the university of Grénoble. The coming four years she will be working on the QuantumLignin project. In this project, she’ll investigate the structure-property relations of lignin building blocks, with the aim of creating an additive model suitable for predicting the properties of mixed lignin samples. With her life motto: “Don’t wait for the perfect moment. Take the moment and make it perfect.” I’m sure we can expect great things to happen in the theoretical lignin field, the coming years.

Welcome to the QuATOMs team, we look forward to your enthusiasm and the intuition you bring to the team.

Permanent link to this article: https://dannyvanpoucke.be/new-quatoms-group-member-minh-thu-bui/

Jan 01 2025

Review of 2024

  • Filed under blog

  • January 1, 2025

Happy 2025

2023 and 2024 have been an intense ride, with both the materiomics program, the tenure track and the research group. Since the previous overview in 2022, the QuATOMs group has seen some growth with the arrival of three new members (Pauline Castenetto, Thijs van Wijk, and Aylin Melan). In addition, Emerick Guillaume defended his PhD on the study of diamond growth.

These are not the only things which happened the last two years, so let us look back at 2023 and 2024 one last time, keeping up with  tradition.

1. Publications: +4 (and currently a handful in progress)

2. Cover publication: +1

Cover Nature Reviews Physics: Accuracy of DFT

3. Project proposals accepted: +2

  • QuantumLignin: Elucidating the interactions of lignin building blocks with their environment for the creation of additive models by means of quantum mechanical modelling.
  • AI-accelerated quantum mechanical modelling of the optical properties of semiconductor materials: from colour centres in diamond to transition-metal oxides.

4. Completed refereeing tasks: +20

  • ACS Photon
  • Journal of Physics D: Applied Physics (2x)
  • Philosophical Transactions (2x)
  • Journal of Materials Chemistry A (2x)
  • Journal of Physical Chemistry (3x)
  • Diamond and Related Materials (11x)

5. Conferences & seminars: +7/+1 (Attended & Organised)

  • SBDD XXVII & SBDD XXVIII, Hasselt University, Belgium, March 15th-17th, 2023 & February 28th-March 1st, 2024 [poster presentations, PhD students & MSc student]
  • EAB-workshop on AI in Higher Education, UHasselt, Belgium, April 24th, 2024 [oral presentation]
  • DFT-2024: 20th International Conference on Density Functional Theory and its Applications, Paris, France, August 25th-30th, 2024 [oral presentation]
  • E-MRS Spring meeting 2023 & 2024, Strassbourg, France, May 29th-June 2nd, 2023 & May 27th-31st, 2024 [oral presentations]
  • Summer School: “Materiomics: Innovative Materials From Healthcare Across Quantum To Sustainable Technologies”, UHasselt, Belgium, September 4th-6th, 2024 [member of Organizating Committee; seminar]
  • NISM seminar: “Extreme Machine Learning – When the average model knows best”  (Prof. L. Henrard), UNamur, Belgium, September 12th, 2024 [invited seminar]

6. Supervised students:

  • BSc Projects Physics: 4
  • MSc Projects Materiomics: 3
  • Internships: 2

7. Hive-STM program:

And now, upward and onward, a new year, a fresh start.

Permanent link to this article: https://dannyvanpoucke.be/review-of-2024/

Dec 17 2024

The devil in the details: lessons from Li6PS5X for robust high-throughput workflows

Authors: Asif Iqbal Bhatti, Sandeep Kumar, Catharina Jaeken, Michael Sluydts, Danny E.P. Vanpoucke, and Stefaan Cottenier
Journal: Journal of Materials Chemistry A 13, 526-539 (2025)
doi: 10.1039/D4TA06603K
IF(2024): 10.7
export: bibtex
pdf: <J.Mat.Chem.A>

 

Graphical Abstract: Schematic representation of the LPS material and the variation of results obtained due to slight changes in settings within a High Throughput workflow.

Abstract

High-throughput computational screening has become a powerful tool in materials science for identifying promising candidates for specific applications. However, the effectiveness of these methods relies heavily on the accuracy and appropriateness of the underlying models and assumptions. In this study, we use the popular argyrodite solid-state electrolyte family Li6PS5X (X = Cl, Br, I) as a case study to critically examine key steps in high-throughput workflows and highlight potential pitfalls. We demonstrate some of these pitfalls by highlighting the importance of careful structural considerations, including symmetry breaking and site disorder, and examine the difference between 0 K thermodynamic stability and finite-temperature stability based on temperature-dependent Gibbs free energy calculations. Furthermore, we explore the implications of these findings for the ranking of candidate materials in a mini-throughput study in a search space of isovalent analogs to Li6PS5Cl. As a result of these findings, our work underscores the need for balanced trade-offs between computational efficiency and accuracy in high-throughput screenings, and offers guidance for designing more robust workflows that can better bridge the gap between computational predictions and experimental realities.

Permanent link to this article: https://dannyvanpoucke.be/2025-paper-thedevilinthedetails-en/

Sep 22 2024

End of summer, and the start of a new academic year.

  • Filed under blog

  • September 22, 2024

Mid September in Hasselt means the start of a new academic year. It brings to an end a summer of doing some unrestricted research. Especially the last month has been extremely busy.

  • The DFT2024 conference in Paris from August 25th until 30th, where I presented our recent work on the GeV defect, which we will be submitting shortly.
  • The materiomics summer school, where I gave a lecture on performing practical quantum mechanical calculations,
  • The public PhD defense of Emerick Guillaume (QuATOMs group member) on the growth of diamond: congratulations Emerick!
  • A seminar at UNamur on “extreme machine learning”, discussing our work on small datasets and some of the work I did this summer on a spray coating dataset.

Today the first week of academic year ended, and I already had the pleasure teaching quantum mechanics and modelling courses to chemistry and materiomics students. We also welcome 2 MSc materiomics students to the group: Brent Motmans and Eleonora Thomas. Brent will be working on an experimental-theoretical project, where the theoretical side will focus on machine learning of his experimental data. Eleonora on the other hand will be combining DFT and machine learning in her study of diamond. A very warm welcome to the QuATOMs group for both.

 

Permanent link to this article: https://dannyvanpoucke.be/end-of-summer-and-the-start-of-a-new-academic-year/

Sep 01 2024

New QuATOMs group member

During the last year, Esin Aylin Melan worked hard at her MSc Thesis within the QuATOMs group. Her research focus was centered on the impact of strain on the zero-phonon-line of the GeV color center in diamond. This work she presented, together with Thijs van Wijk, at the SBDD conference in Hasselt, and was presented as well at both the BPS and EMRS spring meeting of 2024. Before the summer she gave her (very good and enthusiastic) final presentation of the MSc thesis results, bringing her first real research project to good end. (Paper will follow later 🙂 )

Recently, she also received the great news that she was awarded a bilateral PhD Scholarship between UHasselt & UNamur. So from September first, she has started working on the modeling of color centers in diamond and oxides for the coming four years. Welcome to the QuATOMs team, and congratulations on the scholarship. We look forward to the enthusiasm and insights you’ll bring to the team.

Permanent link to this article: https://dannyvanpoucke.be/new-quatoms-group-member/

Jun 21 2024

DigiLignin: Consortium Meeting

Today we had our fourth consortium meeting for the DigiLignin project. Things are moving along nicely, with a clear experimental database almost done by VITO, the Machine Learning model taking shape at UMaastricht, and quantum mechanical modeling providing some first insights.

Permanent link to this article: https://dannyvanpoucke.be/digilignin-c4-en/

Mar 06 2024

First-principles investigation of hydrogen-related reactions on (100)–(2×1)∶H diamond surfaces

Authors: Emerick Y. Guillaume, Danny E. P. Vanpoucke, Rozita Rouzbahani, Luna Pratali Maffei, Matteo Pelucchi, Yoann Olivier, Luc Henrard, & Ken Haenen
Journal: Carbon 222, 118949 (2024)
doi: 10.1016/j.carbon.2024.118949
IF(2022): 10.9
export: bibtex
pdf: <Carbon>

 

Graphical Abstract for Carbon publication on the adsorption of H onto diamond.
Graphical Abstract: (left) Ball-and-stick representation of aH adsorption/desorption reaction mediated through a H radical. (right) Monte Carlo estimates of the H coverage of the diamond surface at different temperatures based on quantum mechanically determined reaction barriers and reaction rates.

Abstract

Hydrogen radical attacks and subsequent hydrogen migrations are considered to play an important role in the atomic-scale mechanisms of diamond chemical vapour deposition growth. We perform a comprehensive analysis of the reactions involving H-radical and vacancies on H-passivated diamond surfaces exposed to hydrogen radical-rich atmosphere. By means of first principles calculations—density functional theory and climbing image nudged elastic band method—transition states related to these mechanisms are identified and characterised. In addition, accurate reaction rates are computed using variational transition state theory. Together, these methods provide—for a broad range of temperatures and hydrogen radical concentrations—a picture of the relative likelihood of the migration or radical attack processes, along with a statistical description of the hydrogen coverage fraction of the (100) H-passivated surface, refining earlier results via a more thorough analysis of the processes at stake. Additionally, the migration of H-vacancy is shown to be anisotropic, and occurring preferentially across the dimer rows of the reconstructed surface. The approach used in this work can be generalised to other crystallographic orientations of diamond surfaces or other semiconductors.

Permanent link to this article: https://dannyvanpoucke.be/2024-paper-hadsorption-emerick-en/

Jan 10 2024

Cover Nature Reviews Physics

Authors: Emanuele Bosoni, Louis Beal, Marnik Bercx, Peter Blaha, Stefan Blügel, Jens Bröder, Martin Callsen, Stefaan Cottenier, Augustin Degomme, Vladimir Dikan, Kristjan Eimre, Espen Flage-Larsen, Marco Fornari, Alberto Garcia, Luigi Genovese, Matteo Giantomassi, Sebastiaan P. Huber, Henning Janssen, Georg Kastlunger, Matthias Krack, Georg Kresse, Thomas D. Kühne, Kurt Lejaeghere, Georg K. H. Madsen, Martijn Marsman, Nicola Marzari, Gregor Michalicek, Hossein Mirhosseini, Tiziano M. A. Müller, Guido Petretto, Chris J. Pickard, Samuel Poncé, Gian-Marco Rignanese, Oleg Rubel, Thomas Ruh, Michael Sluydts, Danny E.P. Vanpoucke, Sudarshan Vijay, Michael Wolloch, Daniel Wortmann, Aliaksandr V. Yakutovich, Jusong Yu, Austin Zadoks, Bonan Zhu, and Giovanni Pizzi
Journal: Nature Reviews Physics 6(1), (2024)
doi: web only
IF(2021): 36.273
export: NA
pdf: <NatRevPhys>

Abstract

The cover of this issue shows an artistic representation of the equations of state of the periodic table elements, calculated using two all-electron codes in each of the 10 crystal structure configurations shown on the table. The cover image is based on the Perspective Article How to verify the precision of density-functional-theory implementations via reproducible and universal workflows by E. Bosoni et al., https://doi.org/10.1038/s42254-023-00655-3.  (The related paper can be found here.)

Cover Nature Reviews Physics: Accuracy of DFT modeling in solids

 

Permanent link to this article: https://dannyvanpoucke.be/paper2024_accuracycover-en/

Dec 22 2023

Materiomics Chronicles: week 13 & 14

Weeks eleven and twelve gave some rest, needed for the last busy week of the semester: week 13. During this week, I have an extra cameo in the first year our materiomics program at UHasselt.

NightCafe's response to the prompt: "Professor teaching quantum chemistry."

NightCafe’s response to the prompt: “Professor teaching quantum chemistry.”

Within the Bachelor of chemistry, the courses introduction to quantum chemistry and quantum and computational chemistry draw to a close, leaving just some last loose to tie up. For the second bachelor students in chemistry, this meant diving into the purely mathematical framework describing the quantum mechanical angular momentum and discovering spin operators are an example, though they do not represent an actual rotating object. Many commutators were calculated and ladder operators were introduced. The third bachelor students in chemistry dove deeper in the quantum chemical modeling of simple molecules, both in theory as well as in computation using a new set of jupyter notebooks during an exercise session.

In the first master materiomics, I had gave the students a short introduction into high-throughput modeling and computational screening approaches during a lecture and exercise class in the course Materials design and synthesis. The students came into contact with materials project via the web-interface and the python API. For the course on Density Functional Theory there was a final guest response lecture, while in the course Machine learning and artificial intelligence in modern materials science a guest lecture on optimal control was provided. During the last response lecture, final questions were addressed.

With week 14 coming to a close, the first semester draws to an end for me. We added another 15h of classes, ~1h of video lecture, and 3h of guest lectures, putting our semester total at 133h of live lectures (excluding guest lectures, obviously). January and February brings the exams for the second quarter and first semester courses.

I wish the students the best of luck with their exams, and I happily look back at surviving this semester.

Permanent link to this article: https://dannyvanpoucke.be/materiomics-chronicles-week-13-14/