Search NASA⌕ Search

Engineering topics

Liu, Shunshun

Publications and source records attributed to Liu, Shunshun.

Integrating adaptive learning with post hoc model explanation and symbolic regression to build interpretable surrogate models

Abstract We develop a materials informatics workflow to build an interpretable surrogate model for micromagnetic simulations. Our goal is to predict the energy barrier of a moving isolated skyrmion in rare-earth-free $$\hbox {Mn}_4$$ Mn 4 N. Our approach integrates adaptive learning with post hoc model explanation and symbolic regression methods. We discuss an unexplored acquisition function (information condensing active learning) within the adaptive learning loop and compare it with the known standard deviation function for efficient navigation of the search space. Model-agnostic post hoc explanation techniques then uncover trends learned by the trained model, which we then leverage to constrain the expressions used for symbolic regression. Graphical abstract

Biswas, Ankita↗

Helimagnetism in the candidate ferroelectric CrI 2

CrI 2 is a van der Waals (vdW) layered material that exhibits helimagnetism that propagates along ribbon chains. This is determined from neutron time-of-flight diffraction measurements. Be low T N = 17 K in the orthorhombic structure, a screw-like helimagnetic order develops with an incommensurate wavevector of q ≈ (0.2492, 0, 0) at 8 K. Using density functional theory (DFT)+U calculations, the J 1 -J 2 model is leveraged to describe the helimagnetism, where J 1 (> 0) and J 2 (< 0) correspond, respectively, to a ferromagnetic nearest neighbor (NN) and antiferromagnetic next nearest neighbor (NNN) intrachain interaction. In conclusion, the DFT+U calculations suggest that orthorhombic CrI 2 satisfies conditions that favor formation of helimagnetic order.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗