硅酸盐学报

Nd³⁺掺杂磷酸盐玻璃因其较大的受激发射截面、高效能量转换效率以及高能量存储密度，在激光武器、光通信和生物医疗等前沿领域具有重要的应用前景。然而，稀土离子掺杂激光玻璃的研发主要依赖经验引导、简单循环的“试错法”模式，存在研发效率低、周期长、成本高等问题，严重阻碍了激光玻璃材料及器件的发展。以Nd³⁺掺杂Li_2O-MgO-Al_2O₃-P_2O₅玻璃为研究对象，利用玻璃组分空间中的邻近玻璃态化合物(NGCs)来预测玻璃的Nd³⁺局域结构特征和发光性能。研究表明，在该玻璃体系中，通过NGCs预测的Nd³⁺局域结构特征参数与分子动力学模拟结果高度一致；在发光性能方面，通过NGCs预测的荧光寿命和受激发射截面值与实验值的最大相对误差仅分别为6.19%和1.72%。基于此方法，成功筛选出了荧光寿命长、受激发射截面高的Nd³⁺掺杂磷酸盐激光玻璃组分。该研究为新型激光玻璃的组分设计提供了一条快速、低成本、高效的新方法。

Introduction Nd³⁺-doped phosphate glasses,utilizing the ~4F_3/2→~4I_11/2 energy-level transition of Nd³⁺ions,achieve 1.06 μm luminescence and have critical applications in optical communications,biomedical engineering,and defense technologies.However,the development of laser glasses depends on empirical trial-and-error approaches,requiring extensive experimentation to generate limited data.This paradigm suffers from inefficiency,prolonged cycles,high costs,and a lack of theoretical guidance.Moreover,the luminescent properties of rare-earth-doped glasses are closely tied to the local structure of the rare-earth ions.The intricate relationship between structure and performance renders most computational models for glass properties ineffective,severely hindering the rapid advancement of laser glasses.It is thus necessary to develop cross-scale computational methods that combine physical interpretability and extrapolation capabilities to enable accurate prediction and inverse design of luminescent properties for broad-composition Nd³⁺-doped phosphate glasses.In this study,Nd³⁺-doped Li_2O-MgO-Al_2O₃-P_2O₅ glasses were prepared.The local micro structure of Nd³⁺in the glass as a statistical ensemble of its local environments in neighboring glassy compounds(NGCs) was described.Based on this theoretical framework,an NGCs model was proposed to quantitatively predict the luminescent properties of Nd³⁺-doped phosphate laser glasses,positing that the glass s luminescent properties could be equal to the statistical average of the corresponding properties of its NGCs.This work could provide a theoretical foundation for quantitatively calculating the local structure and luminescent properties of rare-earth-doped laser glasses.Methods In rare-earth-doped laser glasses,the luminescent properties were determined via the analysis of the local structure of the rare-earth ions.The local structure of rare-earth ions in multicomponent laser glasses as a statistical ensemble of their configurations in NGCs was simulated based on the broken ergodicity theory.The NGCs in the compositional space(i.e.,Li_2O·Al_2O₃·4P_2O₅,9Li_2O·3 Al_2O₃·8P_2O₅,P_2O₅,Li_2O·P_2O₅,Al_2O₃·3P_2O₅,Li_2O·2MgO·P_2O₅,MgO·P_2O₅,Li_2O·6MgO·3P_2O₅,Al_2O₃·P_2O₅,MgO·2P_2O₅ and2MgO·Al_2O₃·P_2O₅) were identified via querying the Materials Project database for the quaternary phosphate system(i.e.,Li_2O-MgO-Al_2O₃-P_2O₅).The local micro structure and luminescent properties of all glass compositions in this system were derived from these 11 NGCs by the NGCs model.The molecular dynamics(MD) simulations were performed by the Large-scale Atomic/Molecular Massively Parallel Simulator(LAMMPS).The Morse potential,suitable for modeling short-range interactions in rare-earth-doped glasses,was employed.The long-range interactions were treated by the Ewald summation method(cutoff radius:12.0 ?),while the short-range interactions were truncated at 8.0 ?.The glass quenching process was simulated at a fixed time step of 2 fs.The initial structure was thermalized at5000 K for 1.0 ns to eliminate memory effects.The system was then cooled to 3000 K in the canonical(NVT) ensemble at 5 K/ps.To simulate the experimental conditions,the system was equilibrated in the isothermal-isobaric(NPT) ensemble at 3000 K for 1.0 ns,allowing simultaneous relaxation of the simulation box dimensions and atomic positions.The further cooling to 300 K was conducted in the NPT ensemble at 0.5 K/ps,with intermediate equilibration steps at 2500,2000,1500,1000 K,and 300 K(1 ns each),respectively.Finally,a 1 ns equilibration in the microcanonical(NVE) ensemble was performed,with atomic coordinates recorded every 5000 steps during the last 500 ps.Results and Discussion The radial distribution function g(r) and structure factor S(q),representing short-and medium-range structural orders,were calculated by both the NGCs model and MD simulations.The results from these methods have remarkable consistency,indicating the NGCs model's capability to quantitatively determine the local structural features of Nd³⁺ in Li_2O-MgO-Al_2O₃-P_2O₅ glasses.Since the luminescent properties of rare-earth-doped glasses are governed by the local coordination environment,this agreement validates the NGCs model for predicting luminescent performance.The NGCs model is further applied to calculate key luminescent properties,i.e.,the emission cross-section(σ_e) and fluorescence lifetime(t) of the ~4F_3/2→~4I_11/2 transition.The σ_e values increase monotonically with Li_2O content,showing a maximum relative deviation of 1.72% from experimental data.For τ that is influenced by non-structural factors such as hydroxyl quenching and Nd³⁺ clustering,the maximum relative error is 6.19%.These results underscore the model's accuracy in predicting luminescent properties.A robust composition-property mapping is established via leveraging this model,enabling efficient screening of high-performance Nd³⁺-doped phosphate glass compositions.A comprehensive analysis of 11,355 valid glass compositions within the glass-forming region reveals an inverse correlation between σ_e and τ,i.e.,compositions with a higher σ_e typically exhibit a shorter τ.However,the model identifies a subset of optimized compositions with both high σ_e and extended τ,corresponding to Al_2O₃(0-7%),MgO(10%-18%),and Li_2O(1%-7%).Conclusions This study applied the NGCs model to analyze the local structure and luminescent properties of Nd³⁺-doped Li_2O-MgO-Al_2O₃-P_2O₅ glasses.The calculated g_Re(r) and S_Re(q),reflecting short-and medium-range orders,aligned closely with the MD simulation results,indicating the model's precision in characterizing Nd³⁺ local structures.The model achieved exceptional accuracy in predicting luminescent properties,with maximum relative errors of 1.72% for σ_e and 6.19% for τ,compared to the experimental data.The systematic screening of the glass-forming region identified optimal compositional ranges(i.e.,Al_2O₃:0-7%,MgO:10%-18%,Li_2O:1%-7%) that could simultaneously maximize σ_e and τ.The NGCs model could provide a groundbreaking approach for designing advanced Nd³⁺-doped phosphate laser glasses via establishing a quantitative link between atomic-scale structures and macroscopic performance.This methodology could accelerate material discovery and reduce reliance on costly experimental iterations,paving an efficient way for the development of ne xt-generation laser mate rials.