Tag: computational materials science

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/

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/

Dec 13 2023

How to verify the precision of density-functional-theory implementations via reproducible and universal workflows

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), 45-58 (2024)
doi: 10.1038/s42254-023-00655-3
IF(2021): 36.273
export: bibtex
pdf: <NatRevPhys>
<ArXiv:2305.17274>

 

“We hope our dataset will be a reference for the field for years to come,” says Giovanni Pizzi, leader of the Materials Software and Data Group at the Paul Scherrer Institute PSI, who led the study. (Image: Paul Scherrer Insitute / Giovanni Pizzi)
Graphical Abstract: “We hope our dataset will be a reference for the field for years to come,” says Giovanni Pizzi, leader of the Materials Software and Data Group at the Paul Scherrer Institute PSI, who led the study. (Image: Paul Scherrer Insitute / Giovanni Pizzi)

Abstract

Density-functional theory methods and codes adopting periodic boundary conditions are extensively used in condensed matter physics and materials science research. In 2016, their precision (how well properties computed with different codes agree among each other) was systematically assessed on elemental crystals: a first crucial step to evaluate the reliability of such computations. In this Expert Recommendation, we discuss recommendations for verification studies aiming at further testing precision and transferability of density-functional-theory computational approaches and codes. We illustrate such recommendations using a greatly expanded protocol covering the whole periodic table from Z = 1 to 96 and characterizing 10 prototypical cubic compounds for each element: four unaries and six oxides, spanning a wide range of coordination numbers and oxidation states. The primary outcome is a reference dataset of 960 equations of state cross-checked between two all-electron codes, then used to verify and improve nine pseudopotential-based approaches. Finally, we discuss the extent to which the current results for total energies can be reused for different goals.

Permanent link to this article: https://dannyvanpoucke.be/paper-aiidaconsortium2023-en/

Nov 26 2023

Materiomics Chronicles: week 9 & 10

With the end of the first quarter in week eight, the nine and tenth week of the academic year were centered around the first batch of exams for the first master students of our materiomics program at UHasselt. For the other students in the second master and bachelor, academic life continued with classes.

Coefficients of the 63-1G basis set for the H and He atom.

Coefficients of the 63-1G basis set for the H and He atom.

The course introduction to quantum chemistry starts to hone in on the first actual fully realistic system: the H atom. But before we get there, the students of the second bachelor chemistry extended their particle on a ring model system to an infinite number of ring systems: i.e. discs, spheres, and balls. Separation of variables has no longer any secrets for them. Now they are ready for reality after many weeks of abstract toy models. The third bachelor students on the other hand had their first ever contact with real practical quantum chemistry (i.e. computational chemistry) during the course quantum and computational chemistry. They learned about Hartree-Fock, the self-consistent field method, basis sets and slater orbitals. They entered this new world with a practical exercise class where, using jupyter notebooks and the psi4 package, they performed their first even quantum chemical calculations. Starting with the trivial H and He atom systems as a start, since for these we have calculated exact solutions during the classes of this course. This way, we learned about the quality of different basis sets and the time of calculations.

In the master materiomics, the first master students had their exams on Fundamentals of materials modeling, and Properties of functional materials, where all showed they understood the topics presented to sufficient degree making them ready for the second quarter. For the second master students, the course on Density Functional Theory held a lecture on the limitations of DFT and a guest lecture on conceptual DFT.

With week 10 drawing to a close, we added another 15h of classes, ~1h of video lecture and 2h of guest lectures, putting our semester total at 106h of live lectures. Upwards and onward to weeks 11 & 12.

Permanent link to this article: https://dannyvanpoucke.be/materiomics-chronicles-week-9-10/

Nov 05 2023

Materiomics Chronicles: week 7

After a relatively chill week six, the seventh week of the academic year ended up being complicated. As it was fall-break the week only consisted of two class days at university. However, primary schools are closed entirely so our son was at home having a holiday, while both parents were trying to juggle classes and project proposal deadlines as well as additional administrative reporting. A second evaluation meeting with the students of our materiomics program at UHasselt took place (second master this time), and also these students appreciated the effort put into creating their classes.

Although there were only two days of teaching, this did not mean there was little work there. The students of the second bachelor in chemistry extended their knowledge of a particle in a box to the model of a particle on a ring, during the course introduction to quantum chemistry. Similar as for a particle in a box, this can be considered a simplified model for a circular molecule like benzene, allowing us to estimate the first excitation quite accurately.

For the course Fundamentals of Materials Modeling, there was a lecture introducing the first master students materiomics into the very basics of machine learning, as well as an exercise session. During these, the students learned about linear regression, decision trees and support vector machines. This class was also open to students of the bachelor programs to get a bit of an idea of the content of the materiomics program. Finally, the first master students also presented the results of their lab on finite element modeling as part of the course Fundamentals of Materials Modeling. They presented flow studies around arrows, reef and car models, as well as heat transfer in complex partially insulated systems, as well as sinking boats. They showed they clearly gained insight through this type of hands-on tasks, which is always a joy to note, resulting in grades reflecting their efforts and insights.

Though this week was rather short, we added another 6h of classes, putting our semester total at 91h of live lectures. Upwards and onward to week 8.

Permanent link to this article: https://dannyvanpoucke.be/materiomics-chronicles-week-7/

Oct 29 2023

Materiomics Chronicles: week 6

After surviving week five, the sixth week of the academic year feels almost relaxing. However, all the effort is worth it, and I was happy to hear the students of our materiomics program at UHasselt appreciate the effort put into creating their classes, during an evaluation meeting.

The evolution of the Z position of a Be atom on Graphene. Periodic cell with 10 Angstrom vacuum along z direction. Z position is given in direct coordinates (0...1), with the graphene sheet positioned at z=0 (=1). The Be atom is van der Waals bonded, and moves through the vacuum to attach to the "bottom" side of the sheet, though originally positioned at the "top" side.

The evolution of the Z position of a Be atom on Graphene. Periodic cell with 10 Angstrom vacuum along z direction. Z position is given in direct coordinates (0…1), with the graphene sheet positioned at z=0 (=1). The Be atom is van der Waals bonded, and moves through the vacuum to attach to the “bottom” side of the sheet, though originally positioned at the “top” side.

Though the week was not as intense as the week before does not mean there were no classes at all. The second bachelor students in chemistry continued their studies of particles in simple potentials though the study of a particle in a square infinite potential well during the course introduction to quantum chemistry. During the course quantum and computational chemistry, the third bachelor chemistry, the He atom was now studied by means of the variational method, introducing the concepts of effective nuclear charge and shielding in a natural way.

While the bachelor students could take a backseat approach during the lectures (except for calculating some bbracket integrals), the master materiomics students had to do most of the heavy lifting during their classes. For the course on Density Functional Theory there was response lecture as well as a lab-session where they studied the dynamics of Be on and around graphene, while the first master students had their second presentation & discussion session on the computational aspects of the papers studied in the course Properties of functional materials.

At the end of this week, we added another 11h of live classes and ~2h of video lectures, putting our semester total at 85h of live lectures. Upwards and onward to week 7.

Permanent link to this article: https://dannyvanpoucke.be/materiomics-chronicles-week-6/