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Primeur weekly 2019-03-25

Special

Meeting the challenges of tomorrow - at scale ...

FocusCoE to support HPC Centres of Excellence for outreach to the broader European HPC community ...

Focus

University of Maribor and XENYA signed contract for an HPC system as part of the national research infrastructure project HPC - RIVR, readying Slovenia for EuroHPC participation ...

Exascale supercomputing

U.S. Department of Energy and Intel to deliver first exascale supercomputer ...

Argonne deepens the Department of Energy's footprint in high-impact computing ...

Crowd computing

NVIDIA announces Jetson Nano: $99 tiny, yet mighty NVIDIA CUDA-X AI computer that runs all AI models ...

Quantum computing

In a new quantum simulator, light behaves like a magnet ...

Long-distance quantum information exchange - success at the nanoscale ...

Middleware

NERSC and NVIDIA to partner on compiler development for Perlmutter system ...

Hardware

DDN to unveil transformative solutions for accelerating AI, analytics and Deep Learning at NVIDIA GTC 2019 ...

NVIDIA introduces new breed of high-performance workstations for millions of data scientists ...

Global computer companies announce NVIDIA-powered enterprise servers optimized for data science ...

Mellanox HDR 200G InfiniBand deep learning acceleration engines demonstrates two times higher performance for Artificial Intelligence (AI) platforms with NVIDIA ...

Altair OptiStruct runs up to 10x faster on NVIDIA GPUs ...

Pure Storage unveils NVIDIA-powered solutions for full spectrum of AI initiatives ...

Preferred Networks builds MN-2, a state-of-the-art supercomputer powered with NVIDIA GPUs ...

Supermicro offers end-to-end portfolio of NVIDIA GPU systems ...

Applications

H5 Data Centers completes a High-Performance Compute (HPC) suite in partnership with Forced Physics Data Center Technology ...

Supercomputers to help supercharge ceramic matrix composite manufacturing ...

A surprising, cascading earthquake ...

Brain-inspired AI inspires insights about the brain and vice versa ...

Supercomputer simulations shed light on how liquid drops combine ...

Novel MD simulation sheds light on mystery of hydrated electron's structure ...

Kicking neural network automation into high gear ...

DOE extends University PPPL contract ...

The Cloud

NVIDIA teams with Amazon Web Services to bring AI to millions of connected devices ...

Novel MD simulation sheds light on mystery of hydrated electron's structure


A novel MD simulation provides conclusive evidence in favor of a persistent tetrahedral cavity made up of four water molecules. Credit: Vladimir Rybkin.
22 Mar 2019 Zurich - The e-aq species is difficult to observe directly because it is short-lived and cannot be separated or concentrated. This rules out using direct structural approaches, diffraction or NMR spectroscopy to explore its structure. Though some properties including spectra in UV and IR-regions and the binding energy have been directly observed, the general lack of direct experimental measurements of the structure of the hydrated electron calls for theory.

Reliable modelling of the hydrated electron is at least as challenging as the experimental approach though and the limitations of the computational approaches applied so far have led to considerable theoretical uncertainty. Researchers have not, for example, been able to agree on whether or not the hydrated electron occupies a cavity. Though most theoretical studies suggest that it does, non-cavity models have also proven accurate. Another point of discussion is linked to the distinguishable surface and bulk structures of the hydrated electron.

In the paper, researchers Vladimir Rybkin and Jan Wilhelm at the University of Zurich and Joost VadeVondele at ETH Zurich and CSCS used the first molecular dynamics simulation of the bulk hydrated electron based on correlated wavefunction theory to provide conclusive evidence in favor of a persistent tetrahedral cavity made up of four water molecules. They also showed that there are no stable noncavity structures in the bulk hydrated electron.

The scientists arrived at their model through careful consideration of what features the most accurate approach must have. They wanted it to be based on molecular dynamics to capture the formation and dynamic transformations of the cavity. They needed a many-body correlated electronic structure level to avoid delocalization error and to allow for the correlation effects that have been found crucial in predicting the solvation of the electron accurately without empirical parameters. They wanted the simulation to be performed in the bulk under periodic boundary conditions to avoid formation of the surface structure and, finally, the method should provide an accurate description of liquid water.

The MD simulation they devised - the very first dynamic simulation of a complex chemical species in the condensed phase at the correlated wave function level of theory - fulfills all of these requirements. This was the first critical step. The second was actually managing to carry it out. Such calculations have been technically impossible until recent advances - including those made in their own groups - have allowed for massively parallel manybody theory calculations in the condensed phase on stateart supercomputers such as those as CSCS. It nonetheless took them about 1 million node hours on the Piz Daint supercomputer, Europe's fastest.

The model showed that a cavity is formed within 250 femtoseconds after the excess electron is added to the unperturbed liquid water. Critically, the simulation failed to find any evidence of noncavity structures of the bulk hydrated electron in either stable or metastable states: this provides much stronger theoretical evidence for the cavity model.

The paper was funded in part by NCCR MARVEL.

Source: National Centre of Competence in Research - NCCR: MARVEL

Back to Table of contents

Primeur weekly 2019-03-25

Special

Meeting the challenges of tomorrow - at scale ...

FocusCoE to support HPC Centres of Excellence for outreach to the broader European HPC community ...

Focus

University of Maribor and XENYA signed contract for an HPC system as part of the national research infrastructure project HPC - RIVR, readying Slovenia for EuroHPC participation ...

Exascale supercomputing

U.S. Department of Energy and Intel to deliver first exascale supercomputer ...

Argonne deepens the Department of Energy's footprint in high-impact computing ...

Crowd computing

NVIDIA announces Jetson Nano: $99 tiny, yet mighty NVIDIA CUDA-X AI computer that runs all AI models ...

Quantum computing

In a new quantum simulator, light behaves like a magnet ...

Long-distance quantum information exchange - success at the nanoscale ...

Middleware

NERSC and NVIDIA to partner on compiler development for Perlmutter system ...

Hardware

DDN to unveil transformative solutions for accelerating AI, analytics and Deep Learning at NVIDIA GTC 2019 ...

NVIDIA introduces new breed of high-performance workstations for millions of data scientists ...

Global computer companies announce NVIDIA-powered enterprise servers optimized for data science ...

Mellanox HDR 200G InfiniBand deep learning acceleration engines demonstrates two times higher performance for Artificial Intelligence (AI) platforms with NVIDIA ...

Altair OptiStruct runs up to 10x faster on NVIDIA GPUs ...

Pure Storage unveils NVIDIA-powered solutions for full spectrum of AI initiatives ...

Preferred Networks builds MN-2, a state-of-the-art supercomputer powered with NVIDIA GPUs ...

Supermicro offers end-to-end portfolio of NVIDIA GPU systems ...

Applications

H5 Data Centers completes a High-Performance Compute (HPC) suite in partnership with Forced Physics Data Center Technology ...

Supercomputers to help supercharge ceramic matrix composite manufacturing ...

A surprising, cascading earthquake ...

Brain-inspired AI inspires insights about the brain and vice versa ...

Supercomputer simulations shed light on how liquid drops combine ...

Novel MD simulation sheds light on mystery of hydrated electron's structure ...

Kicking neural network automation into high gear ...

DOE extends University PPPL contract ...

The Cloud

NVIDIA teams with Amazon Web Services to bring AI to millions of connected devices ...