arXiv subjects

Thiti Bovornratanaraks

Publications and source records attributed to Thiti Bovornratanaraks.

4 recordsLinked to original sources

arXiv2025

CrystalGRW: Generative Modeling of Crystal Structures with Targeted Properties via Geodesic Random Walks

Determining whether a candidate crystalline material is thermodynamically stable depends on identifying its true ground-state structure, a central challenge in computational materials science. We introduce CrystalGRW, a diffusion-based generative model on Riemannian manifolds that proposes novel crystal configurations and can predict stable phases validated by density functional theory. The crystal properties, such as fractional coordinates, atomic types, and lattice matrices, are represented on suitable Riemannian manifolds, ensuring that new predictions generated through the diffusion process preserve the periodicity of crystal structures. We incorporate an equivariant graph neural network to also account for rotational and translational symmetries during the generation process. CrystalGRW demonstrates the ability to generate realistic crystal structures that are close to their ground states with accuracy comparable to existing models, while also enabling conditional control, such as specifying a desired crystallographic point group. These features help accelerate materials discovery and inverse design by offering stable, symmetry-consistent crystal candidates for experimental validation.

cond-mat.mtrl-sci↗

arXiv2023

Diffusion probabilistic models enhance variational autoencoder for crystal structure generative modeling

The crystal diffusion variational autoencoder (CDVAE) is a machine learning model that leverages score matching to generate realistic crystal structures that preserve crystal symmetry. In this study, we leverage novel diffusion probabilistic (DP) models to denoise atomic coordinates rather than adopting the standard score matching approach in CDVAE. Our proposed DP-CDVAE model can reconstruct and generate crystal structures whose qualities are statistically comparable to those of the original CDVAE. Furthermore, notably, when comparing the carbon structures generated by the DP-CDVAE model with relaxed structures obtained from density functional theory calculations, we find that the DP-CDVAE generated structures are remarkably closer to their respective ground states. The energy differences between these structures and the true ground states are, on average, 68.1 meV/atom lower than those generated by the original CDVAE. This significant improvement in the energy accuracy highlights the effectiveness of the DP-CDVAE model in generating crystal structures that better represent their ground-state configurations.

cs.LG↗

arXiv2022

Strong electron-phonon coupling and predicted highest known $T_{c}$ of MXenes revealed in 2H-Mo$_{2}$N under biaxial stress

This letter reports the unexpectedly strong electron-phonon coupling (EPC) and the highest $T_c$ record ($\approx$ 38 K) among the MXenes revealed in the 2H-Mo$_2$N under biaxial stress. At first, its excellent mechanical properties are demonstrated with ideal strength of 37 GPa and elastic modulus of 438 GPa. Subsequently, EPC and corresponding $T_c$ are elucidated upon the dynamically stable range of strain. For strain-free 2H-Mo$_2$N, the EPC constant ($λ$) and $T_c$ are 1.3 and 22.7 K, respectively. This $T_c$ is higher than those of 2H-Mo$_2$C (4.3 K), 1T-Mo$_2$N (16.8 K), and other pristine MXenes. The material exhibits remarkable enhancement in $λ$ and $T_c$ when subject to compressive and tensile stresses. The obvious strong EPC with $λ$ over 2.0 occurs at strains of -4%, -2.5%, and 5%, yielding $T_c$s of 37.8, 35.4, and 28.9 K, respectively. Our findings suggest that the strain-dependent feature and energy levels of electronic bands play an essential role in enhancing EPC. Moreover, the stronger EPC in Mo$_2$N compared with Mo$_2$C is clarified based on lattice vibrations. Therefore, this work paves a practical way for designing 2D superconducting materials using tuning atomic recipes and strain-dependent engineering.

cond-mat.supr-con↗

arXiv2022

Dynamical stability and superconductivity of (Ce,La)H9 under high pressure

Recent experiments have shown that CeH9 and (Ce,La)H9 can be synthesized under high pressure between 90-170GPa and become a superconductor with a high value of superconducting critical temperature (Tc) between 100-200K. In this work, we performed a theoretical study of a (Ce,La)H9 compound where the Ce:La ratio is equal to 1. We used the density functional theory and the {\it ab initio} molecular dynamics (AIMD) method. From the phonon dispersion, there exist some unstable modes around the K-point phonons. Then, we performed AIMD simulation at around 203K and found that the compound becomes stable. The superconducting spectral function can be calculated. We found that $λ$ is as high as 3.0 at 200GPa. By using Allen-Dynes-modified McMillan equation in the strong coupling regime, we found that Tc = 87K at 200GPa.

cond-mat.supr-con↗