[Colloquium] REVISED! Seminar Announcement: Identifying the order-disorder transition of diblock copolymers using metadynamics and massively parallel many-particle simulations on multiple GPUs

[Ninfa Mayorga]

Computation Institute Presentation - Data Lunch Seminar (DLS)

Speaker: Jens Glaser, Department of Chemical Engineering and Materials Science, University of Minnesota
Date: April 12, 2013
Time: 12:00 PM - 1:00 PM
Location: University of Chicago, Searle 240A, 5735 S. Ellis Ave. This talk will be broadcast via Adobe Connect

Identifying the order-disorder transition of diblock copolymers using metadynamics and massively parallel many-particle simulations on multiple GPUs

It has been recently shown that coarse-grained simulation models of AB-diblock copolymers exhibit a form of universality that leads to essentially indistinguishable thermodynamic properties of the disordered phase in very different models. The requirement is that the polymer chains have the same degree of overlap [1]. I will present recent progress in obtaining highly accurate estimates for the order-disorder transition (ODT) in these models. Precise measurements of the ODT are computationally and conceptually challenging, since finite-size effects need to be avoided and slow dynamics arise due to large free energy barriers. I address these two problems by using an accelerated sampling technique, metadynamics, to allow the system to overcome large free energy barriers, and by running large-scale simulations on multiple GPUs.

To enable the use of metadynamics, we developed a flexible multi-mode order parameter to account for multiple possible orientations of the lamellae in the ordered phase. This combination allows for a highly accurate determination of the ODT, which can be validated by using traditional histogram sampling methods with a small system.

Simulations were performed using HOOMD-blue, a versatile GPU-accelerated open-source molecular dynamics code. I will also present on the development of a multi-GPU version of HOOMD-blue, capable of running large-scale simulations on tens to hundreds of GPUs. In my talk, I will describe how communication challenges were overcome using optimized communication algorithms, and present initial performance data measured on the Keeneland and Titan supercomputers. This multi-GPU capability will be released in HOOMD-blue v.1.0.0.

[1] Glaser, J., Qin, J., Medapuram, P., Mueller, M., & Morse, D. (2012). Test of a scaling hypothesis for the structure factor of disordered diblock copolymer melts. Soft Matter, 8(44), 11310-11317.

BIO:
Jens Glaser is a postdoctoral fellow with David Morse at the University of Minnesota,Dept. of Chemical Engineering and Materials Science, where he studies the phase behavior of block copolymers using computer simulations. He completed his doctoral degree in theoretical physics in 2011, with a thesis on 'Networks of semiflexible polymers', under the supervision of Klaus Kroy, University of Leipzig, Germany. In his thesis, he developed a theoretical description of the entangled dynamics in F-actin solutions. During his graduate studies, he became interested in using GPUs for scientific computations, which he also uses for his current research. Glaser holds a fellowship of the Deutsche Forschungsgemeinschaft (German research foundation). 

Information:    Lunch will be provided

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