arXiv subjects

Yifei Mo

Publications and source records attributed to Yifei Mo.

6 recordsLinked to original sources

arXiv2026

FPBench: Application-Oriented Error Decomposition for Foundation Potentials

Foundation potentials (FPs) have emerged as a new basis for atomistic modeling. While their evaluation using average energy and force errors often indicates near-DFT accuracy, their performance in practical computational studies remains inconsistent. Here, we present FPBench, an application-oriented benchmark that evaluates FPs on representative computational tasks. Multiple state-of-the-art FPs are assessed on three fundamental tasks: force prediction for atomistic simulations, energy ranking for substitutional and vacancy orderings, and ion/vacancy migration. Benchmarking these FPs shows that average force and energy errors often fail to predict task performance, revealing substantial differences in practical reliability. FPBench introduces application-oriented error decomposition through metrics that resolve performance according to the physically consequential quantities and configurations governing computational tasks, including the fractions of highly accurate and large-force-error atoms, far-from-equilibrium atoms, relative phase-stability and convex-hull agreement, and along-path errors in ion migration. These error-decomposition metrics identify where FP errors arise within specific computational tasks, providing targeted guidance for model development. FPBench provides an open benchmark, evaluation code, and a public leaderboard for rigorous FP assessment and development.

cond-mat.mtrl-sci↗

arXiv2026

First-Principles Thermodynamic Analysis of Ternary Chalcogenide Phase Change Materials

Chalcogenide phase-change materials (PCMs) are important for nonvolatile memory and reconfigurable photonic technologies. The GeTe-Sb2Te3 system, commonly referred to as GST, is the best-known PCM family, but new PCMs are needed to broaden the accessible property space while retaining fast and reversible switching. Here, we propose a thermodynamic framework, motivated by Ostwald's rule, for understanding and identifying PCMs, since direct modeling of phase-transition dynamics is computationally expensive. Using first-principles calculations, we systematically evaluate the energetics of ternary chalcogenide mixtures and their polymorphs along binary-binary tie lines. By comparing ground-state and metastable structures, we assess phase stability, miscibility, and the likelihood of GST-like polymorph-mediated crystallization pathways across a broad range of ternary chalcogenide mixtures. The calculations reproduce known behavior in GST and related systems and identify several promising candidate mixtures with similar features. These results provide insight into why some PCM systems are more favorable than others and establish a thermodynamic framework for future PCM discovery.

cond-mat.mtrl-sci↗

arXiv2025

Incorporating Si into Sb2Se3: Tailoring Optical Phase Change Materials via Nanocomposites

Chalcogenide-based optical phase change materials (OPCMs) exhibit a large contrast in refractive index when reversibly switched between their stable amorphous and crystalline states. OPCMs have rapidly gained attention due to their versatility as nonvolatile amplitude or phase modulators in various photonic devices. However, open challenges remain, such as achieving reliable response and transparency spanning into the visible spectrum, a combination of properties in which current broadband OPCMs (e.g., Ge2Sb2Se4Te1, Sb2Se3, or Sb2S3) fall short. Discovering novel materials or engineering existing ones is, therefore, crucial in extending the application scope of OPCMs. Here, we use magnetron co-sputtering to study the effects of Si doping into Sb2Se3. We employ ellipsometry, X-ray diffraction, Raman spectroscopy, and scanning and transmission electron microscopy to investigate the effects of Si doping on the optical properties and crystal structure and compare these results with those from first principles calculations. Moreover, we study the crystallization and melt-quenching of thin films via nano-differential scanning calorimetry (NanoDSC). Our experiments demonstrate that 20% Si doping increases the transparency window in both states, specifically to 800 nm (1.55 eV) in the amorphous phase, while reducing power consumption by lowering the melting temperature. However, this reduction comes at the cost of reducing the refractive index contrast between states and slowing the kinetics of the phase transition.

cond-mat.mtrl-sci↗

arXiv2023

Discrepancies and Error Evaluation Metrics for Machine Learning Interatomic Potentials

Machine learning interatomic potentials (MLPs) are a promising technique for atomic modeling. While high accuracy and small errors are widely reported for MLPs, an open concern is whether MLPs can accurately reproduce atomistic dynamics and related physical properties in their applications in molecular dynamics (MD) simulations. In this study, we examine the current state-of-the-art MLPs and uncover a number of discrepancies related to atom dynamics, defects, and rare events (REs), in their MD simulations compared to ab initio methods. Our findings reveal that low averaged errors by current MLP testing are insufficient, leading us to develop novel quantitative metrics that better indicate the accurate prediction of related properties by MLPs in MD simulations. The MLPs optimized by the RE-based evaluation metrics are demonstrated to have improved prediction in multiple properties. The identified errors, the developed evaluation metrics, and the proposed process of developing such metrics are general to MLPs, thus providing valuable guidance for future testing, development, and improvements of accurate, robust, and reliable MLPs for atomistic modeling.

cond-mat.mtrl-sci↗

arXiv2021

Dopant Precursor Adsorption into Single-Dimer Windows: Towards Guided Self-Assembly of Dopant Arrays on Si(100)

Atomically precise dopant arrays in Si are being pursued for solid-state quantum computing applications. We propose a guided self-assembly process to produce atomically precise arrays of single dopant atoms in lieu of lithographic patterning. We leverage the self-assembled c(4x2) structure formed on Br- and I-Si(100) and investigate molecular precursor adsorption into the generated array of single-dimer window (SDW) adsorption sites with density functional theory (DFT). The adsorption of several technologically relevant dopant precursors (PH$_3$, BCl$_3$, AlCl$_3$, GaCl$_3$) into SDWs formed with various resists (H, Cl, Br, I) are explored to identify the effects of steric interactions. PH$_3$ adsorbed without barrier on all resists studied, while BCl$_3$ exhibited the largest adsorption barrier, 0.34 eV, with an I resist. Dense arrays of AlCl$_3$ were found to form within experimentally realizable conditions demonstrating the potential for the proposed use of guided self-assembly for atomically precise fabrication of dopant-based devices.

cond-mat.mtrl-sci↗

arXiv2021

AlCl$_{3}$-dosed Si(100)-2$\times$1: Adsorbates, chlorinated Al chains, and incorporated Al

The adsorption of AlCl$_{3}$ on Si(100) and the effect of annealing the AlCl$_{3}$-dosed substrate was studied to reveal key surface processes for the development of atomic-precision acceptor-doping techniques. This investigation was performed via scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. At room temperature, AlCl$_{3}$ readily adsorbed to the Si substrate dimers and dissociated to form a variety of species. Annealing of the AlCl$_{3}$-dosed substrate at temperatures below 450 $^{\circ}$C produced unique chlorinated aluminum chains (CACs) elongated along the Si(100) dimer row direction. An atomic model for the chains is proposed with supporting DFT calculations. Al was incorporated into the Si substrate upon annealing at 450 $^{\circ}$C and above, and Cl desorption was observed for temperatures beyond 450 $^{\circ}$C. Al-incorporated samples were encapsulated in Si and characterized by secondary ion mass spectrometry (SIMS) depth profiling to quantify the Al atom concentration, which was found to be in excess of 10$^{20}$ cm$^{-3}$ across a $\sim$2.7 nm thick $δ$-doped region. The Al concentration achieved here and the processing parameters utilized promote AlCl$_{3}$ as a viable gaseous precursor for novel acceptor-doped Si materials and devices for quantum computing.

cond-mat.mtrl-sci↗