ITR: Billion-atom Multiscale Simulations on a Grid Priya Vashishta, - PowerPoint PPT Presentation

ITR: Billion-atom Multiscale Simulations on a Grid Priya Vashishta, Rajiv K. Kalia & Aiichiro Nakano Concurrent Computing Laboratory for Materials Simulations Dept. of Physics & Dept. of Computer Science, Louisiana State Univ. Email: {priyav, kalia, nakano}@bit.csc.lsu.edu URL: www.cclms.lsu.edu September 1, 2002: Collaboratory for Multiscale Simulations Departments of Materials Science & Engineering, Physics, Computer Science, and Biomedical Engineering University of Southern California NSF Division of Materials Research Computational Materials Theory Program Review Program Managers: Dr. Bruce Taggart & Dr. Daryl Hess Organizers: Dr. Duane Johnson & Dr. Jeongnim Kim June 20, 2002, Urbana, IL CCLMS CCLMS CCLMS

Outline 1. Multiscale simulation of lattice-mismatched nanopixels & nanomesas 2. Multimillion-atom molecular dynamics simulation of semiconductor nanoparticles 3. GRID computing with latency tolerant algorithms

Concurrent Computing Laboratory for Materials Simulations (CCLMS) Faculty: Priya Vashishta, Rajiv Kalia and Aiichiro Nakano, Postdocs: Paulo Branicio, Bijaya Karki, Hideaki Kikuchi, Sanjay Kodiyalam, Maxim Makeev, Elefterios Lidorikis Dual-Degree Graduate Students: Gürcan Aral, Jabari Lee, Xinlian Liu, Zhen Lu, Brent Neal, Cindy Rountree, Ashish Sharma, Satyavani Vemparala, Weiqiang Wang, Cheng Zhang Undergraduate Students: DeAndra Hayes (Xavier), Paul Miller, Wei Zhao Visitors: Simon de Leeuw (Delft, The Netherlands), Ingvar Ebbsjö (Uppsala, Sweden), Hiroshi Iyetomi (Niigata, Japan), Shuji Ogata (Yamaguchi, Japan), José Rino (São Carlos, Brazil), Fuyuki Shimojo (Hiroshima, Japan) Systems Manager: Monika Lee Coordinator: Jade Ethridge

1,024 CPU System being installed at LSU under the auspices of Louisiana IT initiative.

Hybrid FE/MD Algorithm • FE nodes & MD atoms coincide in the handshake region • Additive hybridization HS Si/Si 3 N 4 nanopixel [1 1 1] [1 1 1] _ _ [2 1 1] [0 1 1]

Si(111)/Si 3 N 4 (0001) Nanopixel Displacement from equilibrium positions Interface Si 3 N 4 full MD Hybrid Si z (top to bottom) [nm] 5 Full MD HS 10 Int . r 15 HS z y Hybrid FE/MD 20 -0.5 0 0.5 r Displacement [Å] 0.0 0.2 0.4 0.6 [Å]

Stress Domains in Si 3 N 4 /Si Nanopixels 70 nm Si 3 N 4 Si -2GPa 2GPa Stress well in Si with a Stress domains in Si crystalline Si 3 N 4 film due to an amorphous due to lattice mismatch Si 3 N 4 film

Epitaxially Grown Quantum Dots - Substrate-encoded size-reducing epitaxy 10nm AlGaAs QD QD GaAs AlGaAs 101 001 GaAs (001) substrate; <100> square mesas A. Madhukar (USC)

Lattice-mismatched Growth of Epitaxial Quantum Dots on Patterned Substrates InAs island formation on Strain relaxation suppresses 2D 3D transformation on a a flat GaAs(001) substrate >1.6 monolayer deposition patterned substrate <100nm [010] cr = 1.6ML cr = 12ML 10 µ m [001] GaAs mesa substrate 14 GaAs/InAs: 7.2% lattice mismatch 12 InAs thickness (ML) 10 A. Madhukar (USC) 8 InAs delivery: 24ML, Base: 75nm Height: 11±1 ML 6 4 InAs MESA SIZE ~ 750 Å GaAs 2 0 GaAs 0 5 10 15 20 25 30 20nm InAs deposition (ML) Self-limiting growth of 12 ML InAs on a patterned substrate

Validation of Interatomic Potentials—GaAs Amorphous GaAs X-ray static 2 structure factor Phonon dispersion 1 Experiment (Strauch & Dorner, '90) amorphous MD 40 Experiment Si 3 N 4 30 [Udron et al., ‘91] 0 0 2 4 6 8 10 (m eV) 20 q (Å -1 ) 10 equency 0 2.5 Theory Ga-As Distance (Å) 40 Fr 30 2.4 20 SiC 10 MD Expt. [Besson et al., '91] 2.3 0 0 10 20 0 10 20 Γ Γ K X L X W L Pressure (GPa) High-pressure phase transition

Atomistic Stress in InAs/GaAs Square Mesa Vertical displacement in the first As layer above the interface • In-plane lattice constant in InAs • Domain formation in larger mesas critical lateral size overlayers exceeds the bulk value at 12 ML self-limiting thickness for 3D island formation

Colloidal Quantum Dots, Rods & Tetrapods Applications • LED, display • Biological labeling • Pressure synthesis of novel materials Collaborator: Paul Alivisatos (Chemistry, Berkeley) 17.5 GPa 22.5 GPa [from Bawendi’s group at MIT] 30 Å High-pressure structural transformation in a GaAs nanocrystal Nucleation at surface Multiple domains

Multiple Domains in a GaAs Nanocrystal Nucleation & growth of high-pressure-phase domains

Domain Fluctuations Third domain’s growth fluctuates with time

Shape Dependence of Transformation Spherical Faceted Faceted Multiple domains Single domain Multiple domains Transformation is sensitive to the initial shape

GRID Computing for a One Billion Atom One Micron Nanopixel • One billion atom simulation for one micron (1000nm) nanopixel. The simulation will be split in two parts - top 200 million atoms on a 256 CPU system and the remaining 800 million on a 1,024 Si/Si 3 N 4 nanopixel CPU system for GRID computing. In GRID computing, quality of service (QoS) and latency issues serious, but not killers. • Main objective is to confirm the nature of hexagonal pattern of stress domains at the interface.

GRID Computing for an Ensemble of 64 Nanoclusters • Nanocrystals in Lennard-Jones liquid • Isothermal-Isobaric simulations • Nanocrystal: 20-60 Å • Pressure: 2.5-25 Gpa • 90% of the particles constitute pressure medium. • 8 to 16 processors optimum for one nanocrystal. • In GRID computing, QoS and latency issues not serious, syncronization needed at pressure change only.

Access Grid Technology for Education and Training of Underrepresented Groups Access Grid

Un de rg ra du a te Edu ca tio n & Tra in in g Co m pu ta tio n a l S cie n ce Wo rks h o p fo r Un de rre pre s e n te d Gro u ps • 1 9 pa rticipa n ts fro m 1 1 in s titu tio n s — Ha m pto n , Cla rk-Atla n ta , Mo re h o u s e , Ja cks o n S ta te , Mis s is s ippi S ta te , Te x a s S o u th e rn , Un iv . o f Te x a s – – Pa n Am e rica n , Xa vie r, Gra m blin g , S o u th e rn & Un iv . o f Lo u is ia n a in Mo n ro e • Activ itie s : Co n s tru ctio n o f a PC clu s te r fro m o ff-th e -s h e lf co m po n e n ts & u s in g th is pa ra lle l m a ch in e fo r a lg o rith m ic a n d s im u la tio n e x e rcis e s .

Summary 1. Multiscale simulation of lattice-mismatched nanopixels & nanomesas 2. Multimillion-atom molecular dynamics simulation of semiconductor nanoparticles 3. GRID computing with latency tolerant algorithms 4. Educational and training activities using access grid CCLMS CCLMS CCLMS

Future: Biologically-inspired Nanostructures Bio-inspired self-assembly of Protein-nanotube-based NASA Information Power Grid epitaxical & nanoparticle nanostructures quantum dots Collaborators: Collaborator: A. Madhukar (USC) Jonathan Trent (NASA) Paul Alivisatos (Berkeley)