Integrated Experimental and Simulation Studies of the Structure and Dissolution Mechanism of Bioactive Glasses

项目名称：生物活性玻璃的结构与溶解机理的综合实验与模拟研究学术优势：将原子模拟与实验（x射线和中子衍射）相结合，获得无机生物活性玻璃的精细玻璃结构模型；这些模型对于更好地了解这些材料的生物活性至关重要。（此处的生物活性是指这些材料与骨骼结合并最终促进骨骼生长和发育的能力，包括成骨细胞分化、增殖、活力和矿化。）固有的复杂性和缺乏长程秩序限制了我们对多组分玻璃结构的理解，而多组分玻璃在生物医学等领域的应用非常重要。通过创新方法的发展以及实验和模型研究的整合，该项目研究了两个具有科学挑战性的问题：复杂的多组分氧化玻璃的结构和这些玻璃在水环境中的溶解机制。经典分子动力学和蒙特卡罗模拟等计算机模拟方法已经产生了丰富的关于玻璃结构的信息，但结果严重依赖于经验势模型的质量，通常需要对实验结果进行验证。另一方面，中子和x射线衍射、EXAFS、红外和拉曼光谱等实验方法可以探测玻璃结构的某些方面，但通常仅限于平均短程结构或相互重叠的结构信息。该方法的新颖之处在于将经典或从头开始的分子动力学模拟与基于散射数据的反蒙特卡罗算法相结合，用于研究玻璃材料的结构，将为生物活性玻璃等复杂的多组分系统生成更精细的中短期结构模型。基于这些结构模型，生物活性玻璃的溶解将使用动力学蒙特卡罗模拟进行研究，并从从头算DFT计算中输入反应能垒和反应途径。所获得的结构模型和溶解机理可以指导更合理和系统地设计用于生物医学应用的新型玻璃组合物和工艺。该项目包括对研究生和本科生进行强化培训，以掌握将多尺度材料建模与最先进的材料表征技术相结合的技能，从而为学生解决具有挑战性的材料问题的未来职业做好准备。更广泛的影响：精制生物活性玻璃在骨修复和修复中的潜在应用代表了本研究可能具有重要更广泛影响的领域。PI描述了一种深思熟虑的承诺，即理解学生如何学习，并提供实践这种理解的各种实践经验。他在一系列模块的基础上开发了一门新的计算材料科学课程，培养学生对材料现象及其潜在机制和实验方法的理解。他使用多媒体通过三维可视化和操作来解释晶体结构，使用原子尺度模拟的电影来说明晶体位错，并通过过渡态理论和能量势垒计算来传达扩散过程。PI让学生参与高级课程的另一个重要方式是使用基于文学的教学。在这里，他将重点放在一组经典的、具有开创性的论文上，通过课堂讨论、家庭作业和考试对它们进行剖析和消化。这教学生如何有效地利用文献，成为合格的研究人员。PI的研究实验室还包括本科生，准备生物活性玻璃样品的学生将有机会访问阿贡参与散射研究。由PI为达拉斯-沃斯堡地区的高中教师组织的材料日向教师介绍了校园内可用的最先进的材料处理，表征和建模设施。他还为沃斯堡学区的拉丁裔和美洲原住民学生提供服务。他目前正在指导德克萨斯州高等数学和科学项目的学生的科学项目，这是一个为选定的高中学生提供的为期两年的寄宿大学入学计划。

ID: MPS/DMR/BMAT(7623) 0907593 PI: Du, Jincheng ORG: University of North TexasTitle: Integrated Experimental and Simulation Studies of the Structure and Dissolution Mechanism of Bioactive GlassesINTELLECTUAL MERIT: Combined atomistic simulations and experimental (X-ray and neutron diffraction) studies will be carried out to obtain refined glass structure models of inorganic bioactive glasses; such models are critical to a better understanding of the bioactivities of these materials. (Bioactivity here denotes the ability of these materials to bond to bone and ultimately to promote bone growth and development, including osteoblast differentiation, proliferation, viability, and mineralization.) The inherent complexity and the lack of long-range order limit our understanding of the structure of multi-component glasses that are important in fields such as biomedical applications. Through development of innovative methodology and integration of experimental and modeling studies, this project attacks two scientifically challenging problems: the structure of the complex multi-component oxide glasses and the dissolution mechanism of these glasses in an aqueous environment. Computer simulation methods such as classical molecular dynamics and Monte Carlo simulations have generated a wealth of information about glass structure, but the results rely heavily on the quality of empirical potential models and validation on experimental results is usually needed. On the other hand, experimental methods such as neutron and X-ray diffraction, EXAFS, and infrared and Raman spectroscopy can probe certain aspects of the structure of glasses but are often limited to averaged short-range structures or mutually overlapping structural information. The novelty of the proposed new method lies in integrating classical or ab initio molecular dynamics simulations with the reverse Monte Carlo algorithm based on scattering data in studying the structure of glass materials, which will generate structural models that have more refined short- and medium-range structures for complex multi-component systems such as bioactive glasses. Based on these structural models, dissolution of bioactive glasses will be studied using kinetic Monte Carlo simulations with input of reaction energy barriers and reaction pathways from ab initio DFT calculations. The structural models and dissolution mechanisms obtained can guide more rational and systematic design of new glass compositions and processes for biomedical applications. This project involves intensive training of graduate and undergraduate students to master skills that combine multiscale materials modeling with state-of-the-art material characterization techniques, and thus prepares students for future careers that involve solving challenging materials problems.BROADER IMPACTS: Potential applications of refined bioactive glasses in restoration and repair of bone represent an arena in which this research may have an important broader impact. The PI describes a thoughtful commitment to understanding how students learn and to providing the kinds of hands-on experiences that implement this understanding. He has developed a new course in Computational Materials Science based on a series of modules that develop students' understanding of materials phenomena and the underlying mechanisms and experimental methods. He uses multimedia to explain crystal structures through three-dimensional visualization and manipulation, to illustrate crystal dislocations using movies of atomic scale simulations, and to convey the diffusion process through transition state theory and energy barrier calculations. Another important way the PI involves students in advanced courses is to use literature based instruction. Here he focuses on a group of classical and seminal papers, dissecting them and digesting them through class discussions, homework, and exams. This teaches the students how to use the literature effectively to become qualified researchers. The PI also involves undergraduates in his research lab, and the students who prepare the bioactive glass samples will have the opportunity to visit Argonne to participate in the scattering studies. A Materials Day organized by the PI for Dallas-Fort Worth area high school teachers introduces the teachers to state of the art materials processing, characterization, and modeling facilities available on his campus. He also conducts outreach to Latino and Native American students in the Fort Worth School District. He is currently guiding science projects for students in the Texas Advanced Math and Science program, a two year residential early college entrance program for selected high school students.