ANR SASHA
SASHA is a 4-year project (2021-2025) founded by the french ANR JCJC program (196,5k€) that focuses on modeling the influence of the surface state of the mechanical properties of nano-objects.
Resume:
When compared to their bulk counterparts, nano-objects are known to benefit of particularly augmented mechanical properties related to their high surface/volume ratio. Nevertheless, this “smaller is stronger” trend is characterized by severe data scattering, merely induced by stress concentration during loading, that impedes quantitative prediction. This behavior cannot be predicted by the current modeling methodology that calls for improper sample geometry, increasing the gap between simulations and experiments. SASHA aims at the development and application of a new nano-by-design methodology to catch stress concentration from the surface of metal and semi-conductor nano-objects (e.g., nanoparticles, nanowires). For the very first time, nano-objects with optimized and realistic surfaces, including surface roughness and chemical alteration (oxidation), will be designed and probed within molecular dynamics and finite-element simulations, via a statistical and quantitative approach. This modeling study will be carried in adequacy with top-of-the-art BCDI and in situ TEM experiments in collaboration with the MATEIS (INSA-Lyon) and IM2NP (Aix-Marseille University) labs. The realistic description of nano-objects surfaces is very critical and might bring a new paradigm in the understanding of mechanical properties at the nanoscale.
24th October, 2023: Pyrough, a tool to build 3D samples with rough surfaces
No matter the scale, surface roughness plays a crucial role in various fields of applications such as mechanical engineering, lubrication, catalysis or machining. In this study, we introduce you to Pyrough, a new tool to build 3D samples with rough surfaces for atomistic and finite-element simulations. Pyrough is open source (you can get it from my Github repository) and relies on the classical roughness theory. Several basic shapes including basic blocks, spheres, grains and wires with self-affine surface asperities are implemented and the object-oriented structure of the program simplifies the implementation of more complex shapes. Virtual sample design is improved using Pyrough, which enables more realistic simulations to be made. Several application examples including e.g., the design of wavy grain boundaries or nanoindentation testing using a roughened indenter tip are presented in ther article.
H. Iteney, J.A.G. Joa, C.L. Bourlot, T.W. Cornelius, O. Thomas, J. Amodeo, Pyrough: A tool to build 3D samples with rough surfaces for atomistic and finite-element simulations, Comput. Phys. Commun. (2023) 108958 (50 days free access) (preprint)
Fig. Pyrough : A tool to build 3D samples with rough surfaces for atomistic and finite-element simulations
16th May, 2023: Coupling DDD and FEM to reach mesoscale modeling of nano-objects (new article)
Modeling the mechanics of nano-objects is generally done using the molecular dynamics (MD) simulation method. However, this approach suffers from size and time scale constraints that make the one-to-one comparison to the experiment particularly difficult.
In Gonzalez-Joa et al. Modelling Simul. Mater. Sci. Eng. 31 (2023) 055003, we use the superposition approach to couple the discrete dislocation dynamics method to finite-element, leading to a new tool called El-Numodis that allows us to get rid of MD limitations. El-Numodis was specially designed to manage nano-objects deformation including dedicated features as a Monte-Carlo-based dislocation nucleation subroutine and the mirror dislocation concept. The article presents the main features of the code as well as numerical test cases and benchmarks going from classical boundary value problems to tensile tests on model thin film.
Check this out : https://iopscience.iop.org/article/10.1088/1361-651X/acd01b or from my Publications page.
Congrats Javier !
Fig. Influence of surfaces on the mechanical response of a thin film under tension
25th April, 2023: COST MecaNano first general meeting at IMDEA Materials in Madrid, Spain
I will be at the COST MecaNano first general meeting at IMDEA Materials in Madrid from tonight to next Friday. I will present our work on the influence of roughness on the mechanics of nano-objects Thursday 27th April at 11:20. Can't wait to be there ;)
6th April, 2023: Hugo and I at the Plasticité conférence in Lyon (France)
Hugo Iteney did present his results on surface roughness and nanomechanics at the Plasticité conference in Lyon (France).
I am also glad to have participated to the conference presenting our work on the coupling between the DDD code Numodis and FEM for nanomechanical applications.
8th March, 2023: Hugo and I at the C'Nano conference next week in Poitiers (France)
Hugo Iteney will present his results about surface roughness and nanomechanics next week (Friday March 17th, 15:15) at the C'Nano conference in Poitiers (France). His talk is entitled "Pyrough : a new tool to model rough samples in atomistic and finite element simulations".
I am also glad to participate to the conference as an invited speaker. I will present a collaborative study between in situ experiments and atomistic simulations entitled "When more is less: the effect of grain boundaries on the mechanical properties of metal nanoparticles".
Here is the link to the conference
UPDATE (March, 15th): due to the strike, we will not be able to join Poitiers and should give our talks using visioconference.
3rd January, 2023: load-controlled versus displacement-controlled nanomechanics, new article in Scripta Materialia
Molecular simulations in nanomechanics are still performed in displacement-controlled mode while many experiments are still force-controlled. Why is this so? It was necessary to change things ;)
In this work published in Scripta Materialia, we control the force imposed by a virtual indentor using a feedback loop driven in Python to compress different types of metallic nanoparticles. The results show significant differences with what was obtained so far with controlled displacement, especially in terms of dislocation densities and dynamics. Congratulations to Hugo Iteney who signs here his first scientific paper.
The article can be found here or in the Publications section of the website.
Fig. Shape and dislocation miscrotructure evolution in a gold nanoparticle under compression using load-controlled (top) and displacement-controlled (bottom) MD simulations. Atoms colored in gold and red respectively refer to surfaces and stacking-fault environments. From Iteney et al. Scripta Materialia 2023.
1st Oct, 2022: with Hugo @MMM10 in Baltimore, USA
Warning, some work related to the ANR SASHA will be presented this week at the MMM10 international conference in Baltimore, USA.
First, I will start presenting the study we did in collaboration with Olivier Thomas and Eugen Rabkin's group about nanoparticles strengthening by coating on monday 11:10 AM (metals at the nanoscale session) recently published in ACS NANO. Then, Hugo will speak about Pyrough, a new tool we developed to model roughness, monday evening at 4:50 PM (metals at the nanoscale session). We will also present posters about force-controlled MD nanocompression and El-Numodis, a new DD/FEM toold we developed during Javier Gonzalez' PhD thesis, in collaboration with Laurent Dupuy and Peter Raback .
The program of the conference can be found here.
Enjoy !
August 22nd 2021: When more is less, new paper in ACS Nano
When more is less: it is well-known that in the case of bulk polycrystalline metals, a reduction in the grain size leads to material hardening, since the grain boundaries represent efficient barriers for slip transfer between the adjacent crystalline grains. In this work published with Pr. Rabkin (Technion Univ.), we used SEM compression tests and MD simulations to show that coating single crystalline Ag nanoparticles with a thin polycrystalline Au layer leads to a weakening of the particles. The results of this study show that adding imperfect material to superstrong single crystalline metal nanoparticles makes them weaker. At the same time, thin nanocrystalline coatings can be employed to improve the formability of metals at the nanoscale.
This study was recently published in ACS Nano:
When More Is Less: Plastic Weakening of Single Crystalline Ag Nanoparticles by the Polycrystalline Au Shell
April 30th 2021: SASHA ANR kick-off : welcome Hugo Iteney !
Hugo just joined our group as a PhD student @IM2NP in the context of the SASHA ANR JCJC project. Hugo will work on modeling nano-objects surface states and their consequences on mechanical properties. Welcome Hugo !!!
March 22nd 2022: Plasticité 2020 conference in Toulouse
Hugo Iteney and I will be in Toulouse (France) next 04-06 April. Hugo will present his first results on modeling the mechanical response of metal nanoparticles under compression.