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arXiv · 2610.25477

NEP-kappa 2.0: A unified framework for phonon transport and nonequilibrium thermalization with machine-learning interatomic potentials

Shixian Liu·Bin Liu·Fei Yin·Gang Wang·Yiming Dong·Yangjun Qin·Alexandra V. Kosyakova·Qiang Xian·Alexander A. Barinov·Ke Xu·Gang Zhang
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Abstract

We present NEP-kappa 2.0, a unified framework that integrates density-functional theory, material-specific machine-learning interatomic potentials, and pretrained force models for advanced phonon calculations. A common workflow enables harmonic lattice dynamics, quasi-harmonic and stochastic self-consistent phonon treatments, three- and four-phonon transport, Wigner population--coherence transport, and time-dependent phonon dynamics. Applications to 3C-SiC, BAs, and Cs$_2$AgInCl$_6$ demonstrate consistent force-model comparisons, finite-temperature renormalization, higher-order scattering, and intermode coherence. Beyond steady-state transport, mode-resolved simulations of selectively excited 3C-SiC reveal that half of the injected optical-phonon energy reaches acoustic modes within approximately 3.75 ps, primarily through one-optical--two-acoustic scattering. Acoustic branches exhibit response times differing by a factor of five, with competing scattering channels producing a transient energy overshoot. Channel-resolved entropy production and persistent nonthermal occupations distinguish interbranch energy redistribution from intrabranch thermalization. The framework connects equilibrium phonon transport with microscopic nonequilibrium energy dynamics.

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Shixian Liu, Bin Liu, Fei Yin, Gang Wang, Yiming Dong, Yangjun Qin, Alexandra V. Kosyakova, Qiang Xian, Alexander A. Barinov, Ke Xu, Gang Zhang. 2026-10-18. NEP-kappa 2.0: A unified framework for phonon transport and nonequilibrium thermalization with machine-learning interatomic potentials. https://arxiv.org/abs/2610.25477

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