I use Blue Waters to simulate an ultracold inferno. Micheline Soley - - PowerPoint PPT Presentation

I use Blue Waters to simulate an ultracold inferno.

Micheline Soley Micheline Soley, Harvard University

Micheline Soley, Harvard University I use Blue Waters to simulate an ultracold inferno. 1 / 15

K K Rb Rb Rb K K Rb

4000 K 14 K

Goal: To introduce the concept of an ultracold inferno in order to make investigation of ultracold reactions possible.

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Standard Approach

Typically, quantum mechanics is used for precise simulation of chemical reactions.

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Standard Approach

However, time-dependent quantum mechanics is computationally intensive and has only been used for a few high-temperature reactions

H2 + OH H + H2O

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Key Challenges

Ultracold reactions cannot be studied with existing quantum techniques because: Vectors scale as T −1/2 with temperature T Arrays scale as ND with system size D

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In contrast, classical mechanics is free of exponential scaling ...but still limited to high temperatures.

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Solution

To make simulation of the ultracold KRb dimer reaction possible, we recognize that it acts like an ultracold inferno.

Image reproduced from MBS, E. J. Heller, Phys. Rev. A, vol. 98, no. 5, pp. 052702, Nov. 2018. Micheline Soley, Harvard University Theoretical Chemistry at a New Frontier 7 / 15

The ultracold inferno enables simulation of the the reaction through semiclassical treatment of the hot intermediate and quantum treatment of the cold products.

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Monte Carlo integration is used to determine the number of ways that atoms can be arranged in the hot intermediate semiclassically. Blue Waters enables the use of quintillions of sampling points via data paralellism.

Images reproduced with permission from nicoguaro and Se Roger via Wikimedia (Creative Commons). Micheline Soley, Harvard University Theoretical Chemistry at a New Frontier 9 / 15

Random matrix theory and R-matrix theory are used to analyze the cold products quantum mechanically.

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

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1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 -

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x

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Parallelization on Blue Waters with ScaLAPACK enables manipulation of large, non-sparse matrices.

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Accomplishments

Preliminary results suggest semiclassical mechanics is not only computationally efficient, but also nearly exact for the hot intermediate. Type Molecules Semiclassical Quantum Analytic Rigid Rotors K2 1.224·105 1.225·105 1.224·105 Rb2 3.06·105 3.058·105 3.063·105 K2, Rb2 1.875·1010 1.874·1010 1.874·1010

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Why It Matters

The combination of classical and quantum mechanics makes possible computational simulation of systems previously considered off-limits.

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Broader Impact

Simulation of the ultracold KRb dimer reaction on Blue Waters has the power to impact a wide range of fields. Theoretical ultracold chemistry Experimental ultracold chemistry Computational chemistry Physics, chemistry, and computer science communities

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Blue Waters Contributions

Education on supercomputing techniques Computational support and resources not otherwise available Discussion with researchers from other fields

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Acknowledgments

Professor Eric J. Heller and Professor Kang-Kuen Ni Blue Waters Project Staff Blue Waters Graduate Research Fellowship National Science Foundation Graduate Research Fellowship under Grant No. DGE1144152

And you, for your attention!

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