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Poonam

Publications and source records attributed to Poonam.

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AUGUR, A flexible and efficient optimization algorithm for identification of optimal adsorption sites

In this paper, we propose a novel flexible optimization pipeline for determining the optimal adsorption sites, named AUGUR (Aware of Uncertainty Graph Unit Regression). Our model combines graph neural networks and Gaussian processes to create a flexible, efficient, symmetry-aware, translation, and rotation-invariant predictor with inbuilt uncertainty quantification. This predictor is then used as a surrogate for a data-efficient Bayesian Optimization scheme to determine the optimal adsorption positions. This pipeline determines the optimal position of large and complicated clusters with far fewer iterations than current state-of-the-art approaches. Further, it does not rely on hand-crafted features and can be seamlessly employed on any molecule without any alterations. Additionally, the pooling properties of graphs allow for the processing of molecules of different sizes by the same model. This allows the energy prediction of computationally demanding systems by a model trained on comparatively smaller and less expensive ones

physics.chem-ph

Computational Orbital Mechanics of Marble Motion on a 3D Printed Surface -- 1. Formal Basis

Simulating curvature due to gravity through warped surfaces is a common visualization aid in Physics education. We reprise a recent experiment exploring orbital trajectories on a precise 3D-printed surface to mimic Newtonian gravity, and elevate this analogy past the status of a mere visualization tool. We present a general analysis approach through which this straightforward experiment can be used to create a reasonably advanced computational orbital mechanics lab at the undergraduate level, creating a convenient hands-on, computational pathway to various non-trivial nuances in this discipline, such as the mean, eccentric, and true anomalies and their computation, Laplace-Runge-Lenz vector conservation, characterization of general orbits, and the extraction of orbital parameters. We show that while the motion of a marble on such a surface does not truly represent a orbital trajectory under Newtonian gravity in a strict theoretical sense, but through a proposed projection procedure, the experimentally recorded trajectories closely resemble the Kepler orbits and approximately respect the known conservation laws for orbital motion. The latter fact is demonstrated through multiple experimentally-recorded elliptical trajectories with wide-ranging eccentricities and semi-major axes. In this first part of this two-part sequence, we lay down the formal basis of this exposition, describing the experiment, its calibration, critical assessment of the results, and the computational procedures for the transformation of raw experimental data into a form useful for orbital analysis.

physics.ed-ph