Scientific Computing Department Seminars
01 Feb 2019
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Guido Giuntoli, Barcelona Supercomputing Centre, Spain.

Host: Charles Moulinec, SCD

 

Monday 29 April at 14:00-15:00

CR3 DL and via VC to R89/S48 in RAL

To join by Zoom see instructions below

 

Development of a fully parallel multi-scale method for composite material problems.

It has taken many years for the FE2 multi-scale method to go from fundamental research to practical applications. The method is used to solve very heterogeneous solid mechanics problems such as the ones encountered in aeronautics when using composite material parts. The reason why the method was not affordable up to now was the huge computational cost required for solving two nested finite element calculations, with one finite element resolution per macro-scale integration point. Fortunately, parallel computing using heterogeneous architectures offers the opportunity to efficiently solve embarrassingly parallel problems such as the ones dealt with during the micro-scale calculation. In this talk we will explain how the FE2 multi-scale method works, show what the main obstacles to tackle are and present some of our attempts to optimise the coupling using GPUs.

 

 

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Ivan Scivetti

Host: Alin M Elena, SCD

 

Friday 3 May at 13:00-14:00

CR3 DL and via VC to R89/S48 in RAL

To join by Zoom see instructions below

 

Electrostatics at metallic surfaces: an old standing density functional problem

 

Ivan Scivetti1;2, Alin M. Elena1, Mats Persson2;3 and Ivan Runggers4

1 Daresbury Laboratory, Sc. Tech. Keckwick Lane, Daresbury, WA4 4AD, Warrington, UK

2 Surface Science Research Centre and Department of Chemistry, University of Liverpool, Liverpool L69 3BX, UK

3 Department of Applied Physics, Chalmers University of Technology, SE-412 96 Goteborg, Sweden

4 National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK

 

E-mail: ivan.scivetti@stfc.ac.uk

 

Almost fifty years ago, the seminal work of N.D. Lang and W. Kohn [1] on metallic surfaces revolutionised the field of surface science, and made of computational research based on Density Functional Theory (DFT) an invaluable tool to support experiments.

Nowadays, most DFT simulations of surfaces are routinely conducted using periodic boundary conditions (PBCs) together with the slab approximation and the pseudo-potential method. Since metals screen any perturbation within a range of approximately 2 Angstroms, only few atomic layers are often considered for the slab models, and this choice is mainly restricted by the amount of atoms that can be included in the simulation. Surprisingly, despite the enormous amount of DFT work over the years, it appears there are no reported studies dedicated to explicitely discuss how the electrostatic response depends on the constraints imposed by PBCs, nor how results are affected by the thickness, chemical composition or charge state of the modelled slabs. Understanding this complex interplay is crucial towards the development of robust semi-classical approaches to circumvent, for example, the well-known limitation of fractional charge transfer at interfaces [2,3].

To this purpose, we apply a new DFT methodology [2] to evaluate the electrostatic response of the low-index facets of lithium, aluminium and silver. Via detailed computations of neutral and charged slabs with different number of atomic layers, we investigate the electrostatics beyond linear response. Analysis of key response parameters allow us not only to revise the range of validity of standard approximations but also to provide an alternative view of the connection between the quantum response and classical electrostatic models.

 

 

[1] Lang N D and Kohn W. Phys. Rev. B 1970, 1(12) 4555-4568; 1971, 3(4) 1215-1223; 1973, 7(8) 3541-3550.

[2] Scivetti I and Persson M. Journal of Physics: Condensed Matter 25 355006 (2013).

[3] Souza A M, Rungger I, Pemmaraju C D, Schwingenschloegl U and Sanvito S. Phys. Rev. B 88(16) 165112 (2013).

 

 

 

TO JOIN BY ZOOM:

**Please turn off your camera and microphones once connected**

 

Join from PC, Mac, Linux, iOS or Android: https://ukri-stfc.zoom.us/j/705824125

 

You can test your connection prior to the meeting here:

https://ukri-stfc.zoom.us/test

 

Or iPhone one-tap :

    United Kingdom: +442039663809,,705824125#  or +442036950088,,705824125#

Or Telephone:

    Dial(for higher quality, dial a number based on your current location):

        United Kingdom: +44 203 966 3809  or +44 203 695 0088

        US: +1 669 900 6833  or +1 408 638 0968  or +1 646 876 9923

    Meeting ID: 705 824 125

    International numbers available: https://zoom.us/u/abzn04SnjE

 

Or an H.323/SIP room system:

    H.323:

        162.255.37.11 (US West)

        162.255.36.11 (US East)

        221.122.88.195 (China)

        115.114.131.7 (India)

        213.19.144.110 (EMEA)

        202.177.207.158 (Australia)

        209.9.211.110 (Hong Kong)

        64.211.144.160 (Brazil)

        69.174.57.160 (Canada)

    Meeting ID: 705 824 125

 

    SIP: 705824125@zoomcrc.com

 

Or Skype for Business (Lync):

    https://ukri-stfc.zoom.us/skype/705824125

 

Or Skype on a SurfaceHub:

    SIP: 705824125@lync.zoom.us

 

 

________________________________________

Georgia Lomas

SCD Admin Support

Scientific Computing Department
Science and Technology Facilities Council

Daresbury Laboratory

Sci-Tech Daresbury

Daresbury
Warrington WA4 4AD
Tel. +44 1925 603225
Fax. +44 1925603634

 

STFC is part of UK Research and Innovation

For more information visit https://stfc.ukri.org/

Contact: Lomas, Georgia (STFC,DL,SC)