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arXiv 2304.01650cond-mat.mtrl-scicond-mat.dis-nn
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构建并评估锂基无序岩盐的机器学习原子间势

Constructing and evaluating machine-learned interatomic potentials for Li-based disordered rocksalts

Vijay Choyal, Nidhish Sagar, Gopalakrishnan Sai Gautam

AI总结:

本研究构建了含10842个构型的DFT数据集,综合评估五种机器学习原子间势在锂基无序岩盐中的性能,明确了各模型的优劣,为新型LDR电极发现及复杂构型体系建模奠定基础。

摘要:

锂基无序岩盐(LDRs)是先进锂离子电池的一类重要正极材料,其复杂的化学空间与构型空间对基于传统密度泛函理论(DFT)的高通量筛选方法构成了挑战。值得注意的是,以原子为中心的机器学习原子间势(MLIPs)为精准建模LDRs这类高度无序体系的势能面提供了极具前景的途径,但目前这类MLIPs在该体系中的性能尚未得到严格探究。本文针对五种MLIPs在LDRs建模中的准确性、可迁移性与训练便捷性开展了综合评估,涵盖的模型包括原子能量网络开发的人工神经网络势(AENET)、高斯近似势(GAP)、谱邻域分析势(SNAP)及其二次扩展版本(qSNAP)、矩张量势(MTP)。具体而言,我们生成了包含10842个无序LiTMO₂和TMO₂构型的DFT计算数据集,其中过渡金属TM为Sc、Ti、V、Cr、Mn、Fe、Co、Ni和/或Cu。重要的是,我们发现AENET在能量预测的准确性和可迁移性方面表现最优,而MTP在原子力预测方面表现最佳。在训练轮次较少时AENET的训练速度最快,但随着训练轮次增加,其训练时间显著上升,同时训练误差相应降低。需要注意的是,AENET和GAP在小数据集上容易过拟合,过拟合程度会随数据集增大而降低。最后我们观察到,与DFT相比,AENET对层状单过渡金属LiTMO₂骨架中的平均锂嵌入电压能给出合理的预测(平均误差约10%)。本研究应为发现新型LDR电极以及建模高熵陶瓷、合金等其他构型复杂体系铺平道路。

英文摘要:

Lithium-based disordered rocksalts (LDRs), which are an important class of cathodes for advanced Li-ion batteries, represent a complex chemical and configurational space for conventional density functional theory (DFT)-based high-throughput screening approaches. Notably, atom-centered machine-learned interatomic potentials (MLIPs) are a promising pathway to accurately model the potential energy surface of highly-disordered systems, such as LDRs, where the performance of such MLIPs have not been rigorously explored yet. Here, we represent a comprehensive evaluation of the accuracy, transferability, and ease of training of five MLIPs in modelling LDRs, including artificial neural network potential developed by the atomic energy network (AENET), Gaussian approximation potential (GAP), spectral neighbor analysis potential (SNAP) and its quadratic extension (qSNAP), and moment tensor potential (MTP). Specifically, we generate a DFT-calculated dataset of 10842 disordered LiTMO$_2$ and TMO$_2$ configurations, where TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and/or Cu. Importantly, we find AENET to be the best in terms of accuracy and transferability for energy predictions, while MTP is the best for atomic forces. While AENET is the fastest to train at low number of epochs, the training time increases significantly as epochs increase, with a corresponding reduction in training errors. Note that AENET and GAP tend to overfit in small datasets, with the extent of overfitting reducing with larger datasets. Finally, we observe AENET to provide reasonable predictions of average Li-intercalation voltages in layered, single-TM LiTMO$_2$ frameworks, compared to DFT ($\sim$10% error on average). Our study should pave the way both for discovering novel LDR electrodes and for modelling other configurationally complex systems, such as high-entropy ceramics and alloys.

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