NpjComput.Mater.：鈣鈦礦合金研究：流程自動化

海歸學者發起的公益學術平臺

分享資訊，整合資源

交流學術，偶爾風月

在材料科學蓬勃發展的程序中，清潔能源需求的激增使金屬鹵化物鈣鈦礦（MHPs）材料在光伏領域備受矚目，其功率轉換效率超 26%。然而，MHPs的內在化學不穩定性是實現持久器件的一個挑戰，制約了耐用光伏裝置的發展。這也促使合金化策略出現，如將Cs陽離子與有機候選物混合形成A_1−xCs_xPbI₃（A = MA，FA）。MHPs 具有複雜多晶型特性，其區域性結構與全域性Pm3m空間群不同，存在多種低對稱結構基序，難以透過 XRD 區分，且它們對合金熱力學穩定性和電子性質影響的匱乏研究。分析MHPs合金陽離子混合影響時，雖有理論方法，但保持從頭算準確性面臨挑戰，因其涉及相對論校正。因此，開發一套自動化流程框架，對捕獲這種多晶型特性並研相關電子結構性質極為迫切。

Fig. 1 | SimStack workflow.

來自巴西巴拉那聯邦大學化學系的Luis
Octavio de Araujo等，提出了一種基於 SimStack 框架的自動化工作流程，運用廣義準化學近似（GQCA）等方法，實現了對A_1-xCs_xPbI₃（A=MA，FA）偽立方合金全面深入的研究。該流程可精確計算合金熱力學性質、相圖、光電特性及功率轉換效率，並納入關鍵相對論效應。作者系統分析了有機和無機陽離子混合對合金結構與電子特性的影響，揭示了陽離子特性對格拉澤旋轉及合金穩定性的作用機制，得到不同成分合金的穩定條件及相關熱力學資料，並計算出了不同合金在特定成分下的功率轉換效率，如MA_1-xCs_xPbI₃（0.50<x<1.00）和A_1-xCs_xPbI₃（0.0<x<0.20）在室溫下的高效率表現。

Fig. 12 | Structures. a Pictorial
representation of the APbI3 (CsPbI3) 2 × 2 × 2 supercell expansion.

該研究不僅明確了成分和多晶型程度對 MHP 合金穩定性和光電效能的關鍵影響，且證實了SimStack工作流程在理解此類材料方面的有效性，為未來鈣鈦礦合金研究及最佳化提供了重要依據，有助於推動其在太陽能電池等領域的發展。該文近期發表於npj Computational Materials10: 146 (2024)，英文標題與摘要如下，點選左下角“閱讀原文”可以自由獲取論文PDF。

Automated workflow for analyzing thermodynamic stability in polymorphic perovskite alloys

Luis Octavio de Araujo, Celso R. C. Rêgo, Wolfgang Wenzel, Maurício Jeomar Piotrowski, Alexandre Cavalheiro Dias & Diego Guedes-Sobrinho

In this first-principles investigation, we explore the polymorphic features of pseudo-cubic alloys, focusing on the impact of mixing organic and inorganic cations on their structural and electronic properties, configurational disorder, and thermodynamic stability. Employing an automated cluster expansion within the generalized quasichemical approximation (GQCA), our results reveal how the effective radius of the organic cation (rMA = 2.15 Å, rFA = 2.53 Å) and its dipole moment (μMA = 2.15 D, μFA = 0.25 D), influences Glazer’s rotations in the A1−xCsxPbI3 (A = MA, FA) sublattice, with MA-based alloy presenting a higher critical temperature (527 K) and being stable for x > 0.60 above 200 K, while its FA analog has a lower critical temperature (427.7 K) and is stable for x < 0.15 above 100 K. Additionally, polymorphic motifs magnify relativistic effects, impacting the thermodynamic behavior of the systems. Our methodology leverages the SimStack framework, an automated scientific workflow that enables the nuanced modeling of polymorphic alloys. This structured approach allows for comprehensive calculations of thermodynamic properties, phase diagrams, optoelectronic insights, and power conversion efficiencies while meticulously incorporating crucial relativistic effects like spin-orbit coupling (SOC) and quasi-particle corrections. Our findings advocate for the rational design of thermodynamically stable compositions in solar cell applications by calculating power conversion efficiencies using a spectroscopic limited maximum efficiency model, from which we obtained high efficiencies of about 28% (31–32%) for MA1−xCsxPbI3 with 0.50 < x < 1.00 (FA1−xCsxPbI3 with 0.0 < x < 0.20) as thermodynamically stable compositions at room temperature. The workflow’s significance is highlighted by a Colab-based notebook, which facilitates the analysis of raw data output, allowing users to delve into the physics of these complex systems. Our work underscores the pivotal role of composition and polymorphic degrees in determining the stability and optoelectronic properties of MHP alloys. It demonstrates the effectiveness of the SimStack workflow in advancing our understanding of these materials.