Abstract: The prediction of material properties based on density-functional theory has become routinely common, thanks, in part, to the steady increase in the number and robustness of available simulation packages. This plurality of codes and methods is both a boon and a burden. While providing great opportunities for cross-verification, these packages adopt different methods, algorithms, and paradigms, making it challenging to choose, master, and efficiently use them.
We demonstrate how developing common interfaces for workflows that automatically compute material properties greatly simplifies interoperability and cross-verification.
We introduce design rules for reusable, code-agnostic, workflow interfaces to compute well-defined material properties, which we implement for eleven quantum engines and use to compute various material properties. Each implementation encodes carefully selected simulation parameters and workflow logic, making the implementer’s expertise of the quantum engine directly available to non-experts. All workflows are made available as open-source and full reproducibility of the workflows is guaranteed through the use of the AiiDA infrastructure.

Info: Common workflows for computing material properties using different quantum engines, S.P. Huber, E. Bosoni, M. Bercx, J. Bröder, A. Degomme, V. Dikan, K. Eimre, E. Flage-Larsen, A. Garcia, L. Genovese, D. Gresch, C. Johnston, G. Petretto, S. Poncé, G. Rignanese, C. J. Sewell, B. Smit, V. Tseplyaev, M. Uhrin, D. Wortmann, A. V. Yakutovich, A. Zadoks, P. Zarabadi-Poor, B. Zhu, N. Marzari & G. Pizzi, npj Computational Materials volume 7, Article number: 136 (2021) | DOI: 10.1038/s41524-021-00594-6 | Open Access

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Abstract: We present TB2J, a Python package for the automatic computation of magnetic interactions, including exchange and Dzyaloshinskii–Moriya, between atoms of magnetic crystals from the results of density functional calculations. The program is based on the Green’s function method with the local rigid spin rotation treated as a perturbation. As input, the package uses the output of either Wannier90, which is interfaced with many density functional theory packages, or of codes based on localized orbitals. One of the main interests of the code is that it requires only one first-principles electronic structure calculation in the non-relativistic case (or three in the relativistic case) and from the primitive cell only to obtain the magnetic interactions up to long distances, instead of first-principles calculations of many different magnetic configurations and large supercells. The output of TB2J can be used directly for the adiabatic magnon band structure and spin dynamics calculations. A minimal user input is needed, which allows for easy integration into high-throughput workflows.

Info: “TB2J: A python package for computing magnetic interaction parameters”, X. He, N. Helbig, M. J. Verstraete, E. Bousquet; Computer Physics Communications, Vol. 264, 107938 (July 2021) | DOI: 10.1016/j.cpc.2021.107938 | Open Access

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We have just published a new paper about “First principles investigation of charge transition levels in monoclinic, orthorhombic, tetragonal and cubic crystallography phase of HfO2“, by MD Nur K. Alam, S. Clima, BJ O’Sullivan, B. Kaczer, G. Pourtois, M. Heyns, J. Van Houdt from our partner IMEC on the Journal of Applied Physics 129, 084102 (2021) | DOI; 10.1063/5.0033957. | Open Access.

Abstract: A first-principles study of native point defects in monoclinic, cubic, two different tetragonal, and five different orthorhombic phases of hafnia (HfO₂) is presented. They include vacancy of tri-coordinated and tetra-coordinated oxygen, metal vacancy, interstitial metal, and interstitial oxygen. Defect formation energy, trap depth, and relaxation energy upon optical excitation of defects are listed. The trap depth of oxygen vacancies shows little variation among different phases compared to other defects. Results of the trap depth are compared against measurements and found to have reasonable agreement.

Info: Nur K Alam, Md., Clima, S., O’Sullivan, B.J., Kaczer, B., Pourtois, G., Heynes, M., Van Houdt, J. (2021), “First principles investigation of charge transition levels in monoclinic, orthorhombic, tetragonal, and cubic crystallographic phases of HfO₂“, Journal of Applied Physics 129, 084102,2021, https://doi.org/10.1063/5.0033957

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Abstract: We present a derivation of the exact expression for Pulay forces in density-functional theory calculations augmented with extended Hubbard functionals and arising from the use of orthogonalized atomic orbitals as projectors for the Hubbard manifold. The derivative of the inverse square root of the orbital overlap matrix is obtained as a closed-form solution of the associated Lyapunov (Sylvester) equation. The expression for the resulting contribution to the forces is presented in the framework of ultrasoft pseudopotentials and the projector-augmented-wave method and using a plane-wave basis set. We have benchmarked the present implementation with respect to finite differences of total energies for the case of NiO, finding excellent agreement. Owing to the accuracy of Hubbard-corrected density-functional theory calculations—provided the Hubbard parameters are computed for the manifold under consideration—the present work paves the way for systematic studies of solid-state and molecular transition-metal and rare-earth compounds.

Info: Timrov, I., Aquilante, F., Binci, L., Cococcioni, M., Marzari, N., “Pulay forces in density-functional theory with extended Hubbard functionals: From nonorthogonalized to orthogonalized manifolds”, Phys. Rev. B 102, 235159, DOI 10.1103/PhysRevB.102.235159

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Abstract: Cloud platforms allow users to execute tasks directly from their web browser and are a key enabling technology not only for commerce but also for computational science. Research software is often developed by scientists with limited experience in (and time for) user interface design, which can make research software difficult to install and use for novices. When combined with the increasing complexity of scientific workflows (involving many steps and software packages), setting up a computational research environment becomes a major entry barrier. AiiDAlab is a web platform that enables computational scientists to package scientific workflows and computational environments and share them with their collaborators and peers. By leveraging the AiiDA workflow manager and its plugin ecosystem, developers get access to a growing range of simulation codes through a python API, coupled with automatic provenance tracking of simulations for full reproducibility. Computational workflows can be bundled together with user-friendly graphical interfaces and made available through the AiiDAlab app store. Being fully compatible with open-science principles, AiiDAlab provides a complete infrastructure for automated workflows and provenance tracking, where incorporating new capabilities becomes intuitive, requiring only Python knowledge.

Info: AiiDAlab – an ecosystem for developing, executing, and sharing scientific workflows, A. V. Yakutovicha, K. Eimre, O. Schütt, L.. Talirza, C. S. Adorf, C. W. Andersen, E. Ditler, D. Du, D. Passerone, B. Smit, N. Marzari, G. Pizzi, C. A. Pignedoli, in Computational Material Science, vol. 188 (2021) | DOI: 10.1016/j.commatsci.2020.110165 | Open Access

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Executive Summary: Over the last two decades, the field of computational science has seen a dramatic shift towards incorporating high-throughput computation and big-data analysis as fundamental pillars of the scientific discovery process. This has necessitated the development of tools and techniques to deal with the generation, storage and processing of large amounts of data. In this work we present an in-depth look at the workflow engine powering AiiDA, a widely adopted, highly flexible and database-backed informatics infrastructure with an emphasis on data reproducibility.

We detail many of the design choices that were made which were informed by several important goals: the ability to scale from running on individual laptops up to high-performance supercomputers, managing jobs with runtimes spanning from fractions of a second to weeks and scaling up to thousands of jobs concurrently, and all this while maximising robustness. In short, AiiDA aims to be a Swiss army knife for high-throughput computational science. As well as the architecture, we outline important API design choices made to give workflow writers a great deal of liberty whilst guiding them towards writing robust and modular workflows, ultimately enabling them to encode their scientific knowledge to the benefit of the wider scientific community.

Info & Download: https://doi.org/10.1016/j.commatsci.2020.110086.

Abstract: In the upcoming process to overcome the limitations of the standard von Neumann architecture, synaptic electronics is gaining a primary role for the development of in-memory computing. In this field, Ge-based compounds have been proposed as switching materials for nonvolatile memory devices and for selectors. By employing the classical molecular dynamics, we study the structural features of both the liquid states at 1500 K and the amorphous phase at 300 K of Ge-rich and Se-rich chalcogenides binary Ge_xSe_1–x systems in the range 0.4 ≤ x ≤ 0.6. The simulations rely on a model of interatomic potentials where ions interact through steric repulsion, as well as Coulomb and charge–dipole interactions given by the large electronic polarizability of Se ions. Our results indicate the formation of temperature-dependent hierarchical structures with short-range local orders and medium-range structures, which vary with the Ge content. Our work demonstrates that nanosecond-long simulations, not accessible via ab initio techniques, are required to obtain a realistic amorphous phase from the melt.

Our classical molecular dynamics simulations are able to describe the profound structural differences between the melt and the glassy structures of GeSe chalcogenides. These results open to the understanding of the interplay between chemical composition, atomic structure, and electrical properties in switching materials.

Info: F. Tavanti, B. Dianat, A. Catellani, and A. Calzolari, “Hierarchical short- and medium-range order structures in amorphous GexSe1-x for selectors applications”, ACS Appl. Elec. Mater. 2, 2961-2969 (2020), DOI 10.1021/acsaelm.0c00581

Discover our INTERSECT publications!

The first papers is “AiiDA 1.0, a scalable computational infrastructure for automated reproducible workflows and data provenance“, by Talirz, L., Kumbhar, S., Passaro, E. et al., including or PI and WP2 coordinator Nicola Marzari from our EPFL partner.

AiiDA is a “(…) robust open-source high-throughput infrastructure addressing the challenges arising from the needs of automated workflow management and data provenance recording“.

The paper introduces developments and capabilities required to reach sustained performance, with AiiDA supporting throughputs of tens of thousands processes/hour, while automatically preserving and storing the full data provenance in a relational database making it queryable and traversable, thus enabling high-performance data analytics. AiiDA is a constituent part of the INTERSECT IM2D box, an interoperable materials-to-device simulation platform for the development of disruptive electronics.

The second paper is “Materials Cloud, a platform for open computational science“, by Huber, S.P., Zoupanos, S., Uhrin, M. et al., including Nicola Marzari.

Materials Cloud is a “(…) platform designed to enable open and seamless sharing of resources for computational science, driven by applications in materials modelling“.

The paper illustrates the Materials Cloud platform ecosystem, with its LEARN, WORK, DISCOVER, EXPLORE, and ARCHIVE sections, and aiming to support researchers throughout the life cycle of a scientific project and to make their research output FAIR and reproducible. AiiDA also manages the interconnection of our INTERSECT IM2D from/to external materials databases, such as Materials Cloud.

Read more about the papers on https://nccr-marvel.ch/highlights/2020-09SciData.
To discover more our INTERSECT advancements, take a look at the most recent published deliverables (M18+1) on our website.

References:
→ Huber, S.P., Zoupanos, S., Uhrin, M. et al. AiiDA 1.0, a scalable computational infrastructure for automated reproducible workflows and data provenance. Sci Data 7, 300 (2020).
→ Talirz, L., Kumbhar, S., Passaro, E. et al. Materials Cloud, a platform for open computational science. Sci Data 7, 299 (2020). 

The paper reports on a theoretical description of work function of TiN, which is one of the most used materials for the realization of electrodes and gates in CMOS devices. Indeed, although the work function is a fundamental quantity in quantum mechanics and also in device physics, as it allows the understanding of band alignment at heterostructures and gap states formation at the metal/semiconductor interface, the role of defects and contaminants is rarely taken into account.

By using first principles simulations, the authors present an extensive study of the work function dependence on nitrogen vacancies and surface oxidation for different TiN surface orientations. The results complement and explain a number of existent experimental data, and provide a useful tool to tailoring transport properties of TiN electrodes in device simulations.

A. Calzolari and A. Catellani, “Controlling the TiN Electrode Work Function at the Atomistic Level: A First Principles Investigation,” in IEEE Access, vol. 8, pp. 156308-156313, 2020, doi: 10.1109/ACCESS.2020.3017726. Read at https://ieeexplore.ieee.org/document/9171237

Info:

Published in: IEEE Access ( Volume: 8 )
Page(s): 156308 – 156313
Date of Publication: 19 August 2020 
Electronic ISSN: 2169-3536
DOI: 10.1109/ACCESS.2020.3017726
Publisher: IEEE 
Funding Agency: 10.13039/501100000780-European Commission (EC) through the H2020-NMBP-TO-IND Project

At the end of our first project period M18+1, we have produced new project deliverables! It was a great way to take stock of the work that has been done and to better target and define the next project activities. Find the new deliverables for each work package following and let us know what you think!

J. F. Morgado, A. Calzolari, N. Marzari, and A. Hashibon (2020): Report on INTERSECT high-level requirements, interoperability interfaces for coupling and linking. Deliverable D1.4 of the H2020 project INTERSECT (final version as of 30/07/2020). EC grant agreement no: 814487, CNR, Modena, Italy. It reports on the overall Interoperable Materials-to-Device (IM2D) architecture and workflows design focusing on specific target end users. Download.

J. F. Morgado, A. Padovani, C. Rosati, A. Calzolari, and A. Hashibon (2020): GUI design and setup. Deliverable D1.5 of the H2020 project INTERSECT (final version as of 30/07/2020). EC grant agreement no: 814487, CNR, Modena, Italy. It describes the initial design of Graphical User Interface (GUI) that will be developed within INTERSECT, as front-end of the Interoperable Material-To-Device Simulation Box (IM2D). Download.

A. Padovani, J. Ocker, B. Kaczer, and A. Calzolari (2020): Atomic defect properties from the electrical measurements on FE-HfO2-devices. Deliverable D3.1 of the H2020 project INTERSECT (final version as of 30/07/2020). EC grant agreement no: 814487, Applied Materials, Reggio Emilia, Italy. It describes the use of the device cycle of the IM2D simulation box to extract material and defect properties from the interpretation of the electrical data measured on ferroelectric devices. Download.

A. Padovani, S. Clima, B. Kackzer, L. Medondjio, X. He, P. Ordejón, and A. Calzolari (2020): Atomic defect properties from the electrical measurements on GeSe OTS selectors. Deliverable D3.2 of the H2020 project INTERSECT (final version as of 28/07/2020). EC grant agreement no: 814487, Applied Materials, Reggio Emilia, Italy. It describes of the use of the device cycle of the IM2D Simulation box to extract material and defect properties from the interpretation of the electrical current-voltage (I-V) characteristics measured on Ovonic Threshold Switching (OTS) selector devices. Download.

V. Lunardelli, D. Tomerini, N. Marzari, A. Calzolari, and A. Padovani (2020): First report on IM2D box evaluation through user feedback based on the FOMs. Deliverable D3.3 of the H2020 project INTERSECT (final version as of 28/07/2020). EC grant agreement no: 814487, AMAT, Reggio Emilia, Italy. It evaluates the IM2D box effectiveness during the project enabling the continuous improvement of the platform. Download.

L. Neri, M. Di Berardo, and A. Calzolari (2020): First report on dissemination and communication activity. Deliverable D4.4 of the H2020 project INTERSECT (final version as of 31/07/2020). EC grant agreement no: 814487, CNR, Modena, Italy. It reports on the initial communication and dissemination activities launch and implementation to promote, diffuse, and share the INTERSECT project and its results. Download.

V. Lunardelli, L. Neri, and A. Calzolari (2020): Innovation Management Plan. Deliverable D4.5 of the H2020 project INTERSECT (final version as of 30/07/2020). EC grant agreement no: 814487, CNR, Modena, Italy. It describes the INTERSECT innovation management plan conceived to monitor the market needs and the technical evolutions throughout the project lifetime, and to plan an exploitation strategy after its end. Download.

V. Lunardelli, A. Calzolari, M. Di Berardo, and L. Neri (2020): Risk assessment and risk-mitigation reports. Deliverable D5.2 of the H2020 project INTERSECT (final version as of 29/07/2020). EC grant agreement no: 814487, CNR, Modena, Italy. Basing on certain identified risks for the INTERSECT project,it describes guidelines and tools to update and monitor threats and setbacks that can affect the development of the project tasks. Download.

All project deliverables, MM6+1 and M12+1 included, are available in our Project report section.