****

**Fundamental Computational Sciences**
***Quantum Chromodynamics*
DOE's Oak Ridge and Los Alamos National Laboratories are using  massively parallel computing systemsfor numerical simulations of  quantum chromodynamics (QCD), the fundamental theory of the  stronginteractions of high energy physics.  Such work can help  unlock fundamental secrets of nature.  Forexample, lattice QCD is a  branch of elementary particle physics that seeks to further  understandingof the properties of quarks and gluons (the most basic  constituents of matter) by computationalmodeling of their  interactions. 
QCD software developed for several parallel systems (including the  Cray Research T3D, IBM SP-2, IntelParagon, Thinking Machines CM- 5, and workstation clusters) provides stress tests for all key  systemfeatures -- integer and floating point operations, inter-node  communications, and I/O.  In oneinstance previously undetected  problems were revealed, and large sections of code are now included in a vendor's diagnostic software. 
http://physics.indiana.edu/~sg/qcd_doe.html
***High Capacity Atomic-Level Simulations for the Design of Materials*
The objective of this NSF-supported Grand Challenge at Caltech is to  develop theoretical methods forpractical computations of the  structures and properties of real materials for use in industrial process design for manufacturing new materials.  There is an  enormous gap between current methods foratomistic simulations  and the level needed to accurately describe the relevant properties  ofindustrially important materials.  The strategy is to transcend  from the most fundamental theory,quantum mechanics, where  simulations are limited to small systems (10 to 20 atoms), through molecular dynamics where systems of a few thousand atoms are  possible, to new techniques suitable forpractical chemical  engineering software directed at complex molecules. 
A potentially significant industrial application for atomistic  simulations is predicting the glasstemperature T of a polymer:   above T the polymer is soft and can be formed, while below T it is stiff.  Industry would like to adjust T to desired values by  manipulating the polymer.  This is doneempirically today, leading to  costly and wasteful experiments.  Excellent predictions of T were recently obtained for a variety of cases (including Teflon) in a  collaboration involving Chevron, BFGoodrich, and Asahi Glass.  The  mechanism controlling T was also explained via the simulations, suggesting that in the future it may be possible to control T by  making specific changes to thepolymer. 
http://www.wag.caltech.edu 
***First Principles Simulation of Materials Properties*
The work on the DOE-funded Grand Challenge in Materials Sciences is  distributed among Oak RidgeNational Laboratory, Brookhaven  National Laboratory, and Ames Laboratory at Iowa State University.  The effort is to use high performance computing resources to design  materials.  A key to designingmaterial for structural, magnetic,  optic, electrical, and high temperature applications is our understanding and ability to control synthesis and processing at the  atomic level.  As many of thecrucial macroscopic properties of  materials actually depend on defects, clusters, and microscopic structures involving hundreds to thousands of atoms, it is only with  the availability of modern highperformance computing systems that  first principles modeling of these structures and relatedmaterials  properties can be undertaken.  To this end a hierarchy of increasingly  accurate andcomputationally intensive techniques have been  developed, tested, and are now being applied --classical molecular  dynamics, tight binding molecular dynamics, and ab initio methods.   Parallelcomputing combined with new algorithms that scale  linearly with the number of atoms are being used tocalculate  efficiently the electronic structure and quantum-mechanical forces  for systems of up to500 atoms for ab initio methods and up to  10,000 atoms for tight binding molecular dynamics using anIntel  Paragon XP/S 35. 
The melting and pressure-temperature phase diagram of carbon is an  example in which conditions aretoo extreme for laboratory  experiments, but in which accurate molecular dynamics simulations  areleading to new insights for understanding natural and artificial  diamond synthesis.  The image belowshows a snapshot of 512 carbon  atoms in a diamond lattice in the process of melting (T > 4000K).  The red atoms indicate four-fold bonded (diamond-like) atoms, the  blue atoms indicate three-fold(graphitic) bonded atoms, and there  are also a number of two-fold and five-fold coordinated atoms. The  large number of three-fold atoms indicates that the liquid phase is  less dense than thefour-fold diamond phase.  This is in contrast to  silicon, in which the liquid phase has a higheraverage coordination  than in the diamond structure.  By running such simulations for the  coexistenceconditions of the solid and liquid phases, the melting  temperatures of diamond as a function ofpressure are determined.******