Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7


DL-LEED
In 1999 CCP3 identified the need for a more accurate, robust and efficient LEED package providing reliable automatic structural determination given measured IV curves. Recent improvements in computer performance allow geometry Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 optimisation to be based on fully dynamical LEED calculations and for the perturbative tensor LEED approach to be used to provide a gradient to guide geometry optimisation. The LEED code has been extensively re-written Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 to produce the new DL-LEED package. CCP3 groups are currently testing a beta-release of the core code. The ease of use of DL-LEED is being addressed through a Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 new interface to the DLVisualize software and in order to take advantage of parallel computers a version parallel over energy points is also being developed.




Task

Delivery

Introduction of tensor LEED option and Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 analytic gradient

Apr ‘00

Parallelisation over energy points

May ‘00

Documentation and testing

June ‘00

Interface to DlVisualize

Aug ‘00

Full release of DL-LEED

Oct ‘00




Code development completed and code distributed through CCP3 library.


For further details see the article in Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 Annex 5: A New Modular Low Energy Diffraction Package – DL_LEED.
DL-PED
Photoelectron diffraction is of growing importance as a technique for solving surface structures due to the brightness of third generation Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 synchrotron radiation sources such as the synchrotron radiation facility, which will be built in the UK. The majority of existing codes are based on cluster models and incomplete treatment of multiple Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 scattering effects. DL staff and D. Saldin will collaborate in the development of a new code, which will provide an accurate and efficient treatment of multiple scattering by exploiting the powerful algorithms developed Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 in the DL-LEED code in conjunction with a treatment of diffuse LEED, which allows disordered surfaces to be studies. A beta-release of the code to the CCP Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 73 and SRRTNet communities is anticipated for January 2001.


A new collaboration involving A. Wander (DL) and D. Saldin (University of Wisconsin-Milwaukee) has been established to develop new methods of interpreting auger electron Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 and photoelectron diffraction. This collaboration has given rise to a new code capable of rapidly evaluating auger electron diffraction data. The next step in the development of the code is the inclusion Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 of matrix elements for the evaluation of photoelectron diffraction data. The code will then be applied to a demonstration project in collaboration with M. Gajdardziska-Josifovska (University of Milwaukee-Wisconsin) who has measured photoelectron diffraction Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 signals from the polar surfaces of MgO. The code will then be documented via a comp. Phys. Comms. article and released to UK academic users.
DL-EXCURV
CCP3 has been approached by Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 the hard x-ray user community, who make extensive use of synchrotron based x-ray adsorption experiments (EXAFS, XANES), to develop and maintain the very widely used EXCURV-98 software Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7. The common use of multiple scattering theory between EXCURV and many of the other programs in the CCP3 library means that significant improvements in EXCURV can be мейд based on the existing Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 experience of CCP3. The benefits for surface structural studies are significant. DL staff will prepare and submit a research proposal requesting funds to support these developments (to be submitted May 2000).


A further flagship Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 grant on the development of methods for the analysis and interpretation of x-ray adsorption spectra has been prepared and submitted to the chemistry committee in collaboration with the hard x-ray users Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 group of the synchrotron radiation source. This grant was funded in December 2001.
VEGAS
New optimisation algorithms for the extraction of surface structures from medium energy ion scattering data at the DL facility will Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 be developed and included in the VEGAS package. The code will be released in April 2000.
CRYSTAL
The first principles package CRYSTAL is the subject of the current CCP3 flagship project which finishes Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 in June 2000. The development of fast analytic gradients will allow the study of complex surface structures and chemical processes at surfaces. In addition a significant effort is being мейд Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 to increase the ease of use of CRYSTAL, in particular: the maintenance and extension of the Cerius2 graphical user interface, the generation of better documentation and tutorial materials and the development of a Gaussian Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 basis set library. These resources are being мейд available via the CRYSTAL WWW pages. The prototype gradients code was released to CCP3 December 1999.




Task

Delivery

Geometry optimisation based on analytic gradients

Mar ‘00

Parallel implementation of Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 gradients

June ‘00

CRYSTAL-2000 release

Sep ‘00



CCP3’s flagship project, ending in May 2000, employed Dr. Klaus Doll as a PDRA who collaborated with Saunders and Harrison at DL in the implementation of fast analytic Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 gradients in CRYSTAL. These have been incorporated into various optimisation strategies and now allow the code to optimise bulk and surface structures while applying symmetry constraints if required. The software has been tested Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 and exploited in a sequence of beta releases (beta8 was introduced in August 2001) and will be placed on general release as CRYSTAL-2001 early in 2002. For more information see the article Report on Computational Science and Engineering Support Activities at Daresbury Laboratory 2000/2001 - 7 in Annex 5: CRYSTAL – 2001 - First Principles Simulations.

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