arXiv subjects

Baishun Yang

Publications and source records attributed to Baishun Yang.

8 recordsLinked to original sources

arXiv2026

Fine-Tuning Small Language Models for Reliable VASP INCAR Generation

Language models can prepare VASP INCAR files from natural-language requests, but so far only large proprietary cloud models come close to handling the tightly coupled, physics-sensitive settings reliably, a dependence that fits poorly with local, high-throughput materials workflows where privacy, cost, and offline deployment matter. We show that a small language model (SLM) can close this gap. The SLM is fine-tuned on reference VASP calculations and paired with VASPGuard, a deterministic post-processor that checks syntax, workflow, and material-dependent constraints; we call the combined model INCAR-SLM. On INCARBench, a benchmark for VASP INCAR generation, INCAR-SLM built on Qwen3-4B outperforms every general-purpose LLM evaluated, exceeding GPT-5.4 by 15.55 points on the 100-point INCAR Score. Most of this gain comes from fine-tuning, with VASPGuard correcting the errors that remain. We further find that model size matters less than expected: once fine-tuning and post-processing are applied, performance saturates at a few billion parameters, and Qwen3-4B outperforms larger models in the same family.

cond-mat.mtrl-sci↗

arXiv2026

INCARBench: A Benchmark for Scientific Configuration in VASP INCAR by Large Language Models

Large language models (LLMs) are increasingly being integrated into first-principles computational workflows, yet their ability to configure scientific calculations remains poorly understood. Here, we introduce INCARBench, a benchmark for evaluating LLMs on input configuration for the Vienna Ab initio Simulation Package (VASP) through both configuration generation and repair tasks. Evaluating 19 model configurations reveals substantial capability differences among current frontier models. While several models achieve high semantic and policy accuracy, task-critical correctness remains substantially lower, demonstrating that parameter-level correctness does not necessarily imply scientifically valid configurations. Failure analysis shows that errors concentrate in physically coupled settings involving DFT+$U$, magnetism, and correlated materials, where multiple constraints must be satisfied simultaneously. Repair evaluation further reveals that correcting incorrect settings and preserving already-valid configurations are distinct capabilities, with configuration preservation remaining a major challenge. These findings establish scientific configuration as a measurable capability of large language models and provide a foundation for developing more reliable AI systems for computational materials science.

cond-mat.mtrl-sci↗

arXiv2025

Giant non-reciprocal band structure effect in a multiferroic material

Multiferroic materials, characterized by the coexistence of ferroelectricity and ferromagnetism, may unveil band structures suggestive of complex phenomena and new functionalities. In this Letter, we analyze the band structure of EuO in its multiferroic phase. Using density functional theory calculations and detailed symmetry analysis, we reveal a previously overlooked non-reciprocal band structure effect, where the electronic energy bands exhibit asymmetry along opposite directions with respect to the special points in the Brillouin zone. This effect, which is enabled by spin-orbit coupling, is giant for the top valence Eu $4f$ bands, and can be switched by external electric or magnetic fields. Furthermore, this results in an enhanced bulk photovoltaic effect. Specifically, our predictions indicate the emergence of a large injection current response to linearly polarized light, resulting in a photoconductivity value several orders of magnitude higher than that reported in any other oxide material. Ultimately, this non-reciprocal band structure effect and the associated large bulk photovoltaic response may be general phenomena emerging not just in EuO but also in other multiferroics or magnetoelectrics, potentially providing new cross-functionalities.

cond-mat.mtrl-sci↗

arXiv2024

Emergence of Topological Bimerons in Monolayer CrSBr

The rich and fascinating physics of topological spin textures in van der Waals two-dimensional magnets has motivated recent growing interests, though a comprehensive understanding remains elusive. Here, in atomistic simulations on monolayer CrSBr, we find two magnetic phases emerging under non-equilibrium conditions at distinct temperatures, a standard ferromagnetic transition Tc and a lower temperature T*. Moreover, the real-space analysis of the spin texture reveals the emergence of metastable topological bimeron defects below T*, showing an algebraic-like decaying spin-spin correlation function. The Dzyaloshinskii-Moriya interaction, induced by the local site asymmetry in the centrosymmetric CrSBr monolayer, is proved to be the origin of the bimerons formation. Furthermore, the increasing bimerons density upon increasing the cooling rate follows a Kibble-Zurek behavior, suggesting a handle to drive and control topological bimerons below T*. Our results put forward CrSBr as an important candidate for the investigation of the dynamical behavior of bimerons in vdW magnets.

cond-mat.mtrl-sci↗

arXiv2023

Moiré Magnetic Exchange Interactions in Twisted Magnets

Besides moiré superlattice, twisting can also generate moiré magnetic exchange interactions (MMEIs) in van der Waals magnets. However, due to the extreme complexity and twist-angle-dependent sensitivity, all existing models fail to capture the MMEIs, preventing the understanding of MMEIs-induced new physics. Here, we develop a microscopic moiré spin Hamiltonian that enables the effective description of MMEIs via a sliding-mapping approach in twisted magnets, as demonstrated in twisted bilayer CrI3. Unexpectedly, we discover that the emergence of MMEIs can create an unprecedented magnetic skyrmion bubble (SkB) with non-conversed helicity, named as moiré-type SkB, representing a unique spin texture solely generated by MMEIs and ready to be detected under the current experimental conditions. Importantly, the size and population of SkBs can be finely controlled by twist angle, a key step for skyrmion-based quantum computing and information storage. Furthermore, we reveal that the MMEIs can be effectively manipulated by the substrate-induced interfacial Dzyaloshinskii-Moriya interaction, modulating the twist-angle-dependent magnetic phase diagram, which solves the outstanding disagreements between prior theories and experiments and verifies our theory.

cond-mat.mtrl-sci↗

arXiv2020

Realization of Semiconducting Layered Multiferroic Heterojunctions via Asymmetrical Magnetoelectric Coupling

Two-dimensional (2D) semiconducting multiferroics that can effectively couple magnetic and polarization (P) orders have great interest for both fundamental research and technological applications in nanoscale, which are, however, rare in nature. In this study, we propose a general mechanism to realize semiconducting 2D multiferroics via vdW heterojunction engineering, as demonstrated in a typical heterostructure consisting of magnetic bilayer CrI3 (bi-CrI3) and ferroelectric monolayer In2Se3. Interestingly, the novel indirect orbital coupling between Se 4p and Cr 3d orbitals, intermediated by the interfacial I 5p orbitals, are switchable in the opposite P configurations, resulting in an unexpected mechanism of strong asymmetrical magnetoelectric coupling. Therefore, along with the noticeable ferroelectric energy barrier induced by In2Se3, the realization of opposite magnetic orders in opposite P configurations can eventually result in the novel multiferroicity in bi-CrI3/In2Se3. Finally, we demonstrate that our mechanism can generally be applied to design other vdW multiferroics even with tunable layer thickness.

cond-mat.mtrl-sci↗

arXiv2020

Perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interaction at an oxide/ferromagnetic metal interface

We report on the study of both perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interaction (DMI) at an oxide/ferromagnetic metal (FM) interface, i.e. BaTiO3 (BTO)/CoFeB. Thanks to the functional properties of the BTO film and the capability to precisely control its growth, we are able to distinguish the dominant role of the oxide termination (TiO2 vs BaO), from the moderate effect of ferroelectric polarization in the BTO film, on the PMA and DMI at the oxide/FM interface. We find that the interfacial magnetic anisotropy energy of the BaO-BTO/CoFeB structure is two times larger than that of the TiO2-BTO/CoFeB, while the DMI of the TiO2-BTO/CoFeB interface is larger. We explain the observed phenomena by first-principles calculations, which ascribe them to the different electronic states around the Fermi level at the oxide/ferromagnetic metal interfaces and the different spin-flip processes. This study paves the way for further investigation of the PMA and DMI at various oxide/FM structures and thus their applications in the promising field of energy-efficient devices.

cond-mat.mtrl-sci↗

arXiv2019

Reversible control of Dzyaloshinskii-Moriya interaction at graphene/Co interface via hydrogen absorption

Using first-principles calculations, we investigate the impact of hydrogenation on the Dzyaloshinskii-Moriya interaction (DMI) at graphene/Co interface. We find that both the magnitude and chirality of DMI can be controlled via hydrogenation absorbed on graphene surface. Our analysis using density of states combined with first-order perturbation theory reveals that the spin splitting and the occupation of Co-d orbitals, especially the dxz and dz2 states, play a crucial role in defining the magnitude and the chirality of DMI. Moreover, we find that the DMI oscillates with a period of two atomic layers as a function of Co thickness what could be explained by analysis of out-of-plane of Co orbitals. Our work elucidates the underlying mechanisms of interfacial DMI origin and provides an alternative route of its control for spintronic applications.

cond-mat.mtrl-sci↗