Fixing Interatomic Potentials using Multiscale Modeling: Ad Hoc Schemes for Coupling Atomic and Continuum Simulations

2008 ◽  
pp. 141-155
Author(s):  
Clifford W. Padgett ◽  
J. David Schall ◽  
J. David J. Wesley ◽  
J. David Crill ◽  
Donald W. Brenner
Keyword(s):  
Multiscale Modeling ◽  
Ad Hoc ◽  
Interatomic Potentials

Atomistic Simulations for Multiscale Modeling in bcc Metals

1999 ◽  
Vol 121 (2) ◽  
pp. 120-125 ◽  
Author(s):  
John A. Moriarty ◽  
Wei Xu ◽  
Per So¨derlind ◽  
James Belak ◽  
Lin H. Yang ◽  
...  
Keyword(s):  
Multiscale Modeling ◽  
Strength Properties ◽  
Peierls Stress ◽  
Boundary Structure ◽  
Atomistic Simulations ◽  
Interatomic Potentials ◽  
Ideal Strength ◽  
Bcc Metals ◽  
Kink Pair ◽  
Grain Boundary Structure

Quantum-based atomistic simulations are being used to study fundamental deformation and defect properties relevant to the multiscale modeling of plasticity in bcc metals at both ambient and extreme conditions. Ab initio electronic-structure calculations on the elastic and ideal-strength properties of Ta and Mo help constrain and validate many-body interatomic potentials used to study grain boundaries and dislocations. The predicted Σ5 (310) [100] grain boundary structure for Mo has recently been confirmed in HREM measurements. The core structure, γ surfaces, Peierls stress, and kink-pair formation energies associated with the motion of a/2〈111〉 screw dislocations in Ta and Mo have also been calculated. Dislocation mobility and dislocation junction formation and breaking are currently under investigation.

scholarly journals First‐Principles Multiscale Modeling of Mechanical Properties in Graphene/Borophene Heterostructures Empowered by Machine‐Learning Interatomic Potentials

2021 ◽  
pp. 2102807
Author(s):  
Bohayra Mortazavi ◽  
Mohammad Silani ◽  
Evgeny V. Podryabinkin ◽  
Timon Rabczuk ◽  
Xiaoying Zhuang ◽  
...  
Keyword(s):  
Machine Learning ◽  
Mechanical Properties ◽  
Multiscale Modeling ◽  
First Principles ◽  
Interatomic Potentials

scholarly journals Machine-learning interatomic potentials enable first-principles multiscale modeling of lattice thermal conductivity in graphene/borophene heterostructures

2020 ◽  
Vol 7 (9) ◽  
pp. 2359-2367 ◽  
Author(s):  
Bohayra Mortazavi ◽  
Evgeny V. Podryabinkin ◽  
Stephan Roche ◽  
Timon Rabczuk ◽  
Xiaoying Zhuang ◽  
...  
Keyword(s):  
Machine Learning ◽  
Thermal Conductivity ◽  
Multiscale Modeling ◽  
First Principles ◽  
Lattice Thermal Conductivity ◽  
Interatomic Potentials ◽  
The Continuum

We highlight that machine-learning interatomic potentials trained over short AIMD trajectories enable first-principles multiscale modeling, bridging DFT level accuracy to the continuum level and empowering the study of complex/novel nanostructures.

scholarly journals Multiscale Modeling of Dislocation Processes in Bcc Tantalum: Bridging Atomistic and Mesoscale Simulations

2000 ◽  
Vol 653 ◽  
Author(s):  
L. H. Yang ◽  
Meijie Tang ◽  
John A. Moriarty
Keyword(s):  
Plastic Deformation ◽  
Multiscale Modeling ◽  
Activation Enthalpy ◽  
Analytic Form ◽  
Simulation Method ◽  
Dislocation Dynamics ◽  
Atomic Scale ◽  
Interatomic Potentials ◽  
Screw Dislocations ◽  
Stress Dependent

AbstractPlastic deformation in bcc metals at low temperatures and high-strain rates is controlled by the motion of a/2<111> screw dislocations, and understanding the fundamental atomistic processes of this motion is essential to develop predictive multiscale models of crystal plasticity. The multiscale modeling approach presented here for bcc Ta is based on information passing, where results of simulations at the atomic scale are used in simulations of plastic deformation at mesoscopic length scales via dislocation dynamics (DD). The relevant core properties of a/2<111> screw dislocations in Ta have been obtained using quantum-based interatomic potentials derived from model generalized pseudopotential theory and an ab-initio data base together with an accurate Green's-function simulation method that implements flexible boundary conditions. In particular, the stress-dependent activation enthalpy for the lowest-energy kink-pair mechanism has been calculated and fitted to a revealing analytic form. This is the critical quantity determining dislocation mobility in the DD simulations, and the present activation enthalpy is found to be in good agreement with the previous empirical form used to explain the temperature dependence of the yield stress.

scholarly journals Robust quantum-based interatomic potentials for multiscale modeling in transition metals

2006 ◽  
Vol 21 (3) ◽  
pp. 563-573 ◽  
Author(s):  
John A. Moriarty ◽  
Lorin X. Benedict ◽  
James N. Glosli ◽  
Randolph Q. Hood ◽  
Daniel A. Orlikowski ◽  
...  
Keyword(s):  
Transition Metals ◽  
Multiscale Modeling ◽  
Density Functional ◽  
Large Scale ◽  
Dislocation Core ◽  
Dislocation Dynamics ◽  
Interatomic Potentials ◽  
Dynamic Simulations ◽  
Wide Range ◽  
Dynamics Simulations

First-principles generalized pseudopotential theory (GPT) provides a fundamental basis for transferable multi-ion interatomic potentials in transition metals and alloys within density-functional quantum mechanics. In the central body-centered cubic (bcc) metals, where multi-ion angular forces are important to materials properties, simplified model GPT (MGPT) potentials have been developed based on canonical d bands to allow analytic forms and large-scale atomistic simulations. Robust, advanced-generation MGPT potentials have now been obtained for Ta and Mo and successfully applied to a wide range of structural, thermodynamic, defect, and mechanical properties at both ambient and extreme conditions. Selected applications to multiscale modeling discussed here include dislocation core structure and mobility, atomistically informed dislocation dynamics simulations of plasticity, and thermoelasticity and high-pressure strength modeling. Recent algorithm improvements have provided a more general matrix representation of MGPT beyond canonical bands, allowing improved accuracy and extension to f-electron actinide metals, an order of magnitude increase in computational speed for dynamic simulations, and the development of temperature-dependent potentials.

Die COVID-19-Pandemie im akutstationären Setting aus Sicht von Führungspersonen und Hygienefachkräften in der Pflege

Pflege ◽  
2020 ◽  
Vol 33 (5) ◽  
pp. 289-298
Author(s):  
Katharina Silies ◽  
Angelika Schley ◽  
Janna Sill ◽  
Steffen Fleischer ◽  
Martin Müller ◽  
...  
Keyword(s):  
Ad Hoc ◽  
Qualitative Studie ◽  
Skill Mix ◽  
Task Forces

Zusammenfassung. Hintergrund: Die COVID-19-Pandemie ist eine Ausnahmesituation ohne Präzedenz und erforderte zahlreiche Ad-hoc-Anpassungen in den Strukturen und Prozessen der akutstationären Versorgung. Ziel: Ziel war es zu untersuchen, wie aus Sicht von Führungspersonen und Hygienefachkräften in der Pflege die stationäre Akutversorgung durch die Pandemiesituation beeinflusst wurde und welche Implikationen sich daraus für die Zukunft ergeben. Methoden: Qualitative Studie bestehend aus semistrukturierten Interviews mit fünf Verantwortlichen des leitenden Pflegemanagements und drei Hygienefachkräften in vier Krankenhäusern in Deutschland. Die Interviews wurden mittels qualitativer Inhaltsanalyse ausgewertet. Ergebnisse: Die Befragten beschrieben den auf die prioritäre Versorgung von COVID-19-Fällen hin umstrukturierten Klinikalltag. Herausforderungen waren Unsicherheit und Angst bei den Mitarbeiter_innen, relative Ressourcenknappheit von Material und Personal und die schnelle Umsetzung neuer Anforderungen an die Versorgungleistung. Dem wurde durch gezielte Kommunikation und Information, massive Anstrengungen zur Sicherung der Ressourcen und koordinierte Steuerung aller Prozesse durch bereichsübergreifende, interprofessionelle Task Forces begegnet. Schlussfolgerungen: Die in der COVID-19-Pandemie vorgenommenen Anpassungen zeigen Entwicklungspotenziale für die zukünftige Routineversorgung auf, z. B. könnten neue Arbeits- und Skill Mix-Modelle aufgegriffen werden. Für die Konkretisierung praktischer Implikationen sind vertiefende Analysen der Daten mit zeitlichem Abstand erforderlich.

Tests und Tools

2006 ◽  
Vol 5 (2) ◽  
pp. 68-71 ◽  
Author(s):  
Simone Kauffeld
Keyword(s):  
Ad Hoc ◽  
Non Profit

Zusammenfassung. Der FEO, der in Kooperation mit betrieblichen Praktikern entwickelt wurde, dient der Erfassung des Organisationsklimas. Er umfasst 82 Items und bildet 12 Skalen ab. Eine Stärke des FEO im Gegensatz zu ad hoc entwickelten Befragungsinstrumenten sind die Vergleichsdaten, die für Profit- und Non-Profit-Organisationen bereit gestellt werden. Kritisch diskutiert wird die theoretische Verortung, die Anwenderfreundlichkeit sowie der Nutzen der individuellen Auswertung. Die konsensuale, konvergente, diskriminante und kriterienbezogene Validierung steht aus.

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