一类有序-无序层次结构固体的研究

The structurally disordered matter has been a challenging topic in solid-state physics. Disorder has an immense possibility, that starting from a perfectly ordered structure or completely disordered structure only a limited number of problems could be handled. If a more suitable “intermediately-ordered structure”, which to some extend is also able to be mathematically formulated, is available to act as the starting point, then a large variety of delicate condensed-matter problems may hopefully be better resolved. Based on the research practice on condensed matter physics in the past decade, the applicant has noticed that there is a category of order-disorder hierarchically structured solids, in which an ordered frame system is always present while the disorder appears on another level. The disorder may arise in three distinct ways, namely, from the irregularity of the bond length, bond angle or the orientational mismatch of the multi-atom motifs, or from the random partial occupation of the augmented lattice points, or from the transition from the point-group symmetry to the translational symmetry as occurs in the developmental stage of microcrystals. The order- disorder hierarchically structured solids may manifest negative thermal expansion coefficient, history-dependent phase transition and other anomalies. With the current application we intend to carry out systematical investigation on the order- disorder hierarchically structured solids, of which the samples are the ones like ZrW2O8, Sc2(MoO4)3 and ice crystals (first class), Mn3NAx(A is a metal element) thin films (second class), and Au/Ag microcrystals (third class). From the theoretical aspect we will explore the possibility of mathematical description and calculation of the atomic/electronic structure, and of the characteristic functions for spectroscopic data evaluation. As to experimental investigation, high-quality samples of large crystal for ZrW2O8, Sc2(MoO4)3, ZrV2O7 and alike, Mn3NAx thin films and Au/Ag microcrystals，and icicles will be prepared, and high-resolution atomic images and diffraction patterns will be obtained, the temperature-dependence of structural constants, electrical resistance, specific heat and many other physical properties will be measured so as to establish the structure-property correlation, and so forth. We wish our work in this direction may inspire enthusiasm towards the research of the order-disorder hierarchically structured solids.

无序结构研究一直是固体物理学难题, 从完全有序或无序出发加微扰只能处理有限的问题，若从恰当的中度有序出发则能极大拓展可解决问题的范围。我们发现存在一类有序-无序层次结构固体，有序晶格框架和无序单元在不同层面上。无序可表现为格点上多原子基元之键长或取向的不规则；母晶格之外格点的随机占据；或者微晶发育过程从点群对称向平移对称过渡诱发的无序。此类固体表现出热缩冷涨、途径依赖相变等性质反常。本项目拟针对以ZrW2O8、冰、Mn3NAx (A为杂质金属)薄膜和金/银微晶为代表的三类有序-无序层次结构固体开展系统研究，理论上探索这类结构物质的原子/电子结构及与谱学相关的特征函数之描述和计算可能性，制备高质量ZrW2O8等晶体、Mn3NAx薄膜和金银微晶样品，获得高品质原子图像、衍射花样和近邻原子构型, 测定结构常数、比热、电导率等物性随温度的变化，建立起结构-物性关联，为此类结构固体的研究奠定良好开端

无序结构研究一直是固体物理学难题, 从完全有序或无序出发加微扰只能处理有限的问题，若从恰当的中度有序出发则能极大拓展可解决问题的范围。我们发现存在一类有序-无序层次结构固体，有序晶格框架和无序单元在不同层面上。无序可表现为格点上多原子基元之键长或取向的不规则；母晶格之外格点的随机占据；或者微晶发育过程从点群对称向平移对称过渡诱发的无序。此类固体表现出热缩冷涨、途径依赖相变等性质反常。本项目针对以Mn3NAx (A为杂质金属)薄膜、金/银微晶颗粒和ZrW2O8薄膜为代表的三类有序-无序层次结构固体开展系统研究，制备高质量ZrW2O8等晶体、Mn3NAx薄膜和金银微晶样品，研究生长机理，并测定结构常数、比热、电导率等物性随温度的变化，建立起结构-物性的关联。Mn3Mn1−xPdxN体系中获得高质量薄膜样品，全面研究了其结构，不仅获得了正的磁电阻，而且在电阻变化仅仅加倍的层次上获得了金属-半导体相变。 获得了完美的正十二面体和正二十面体的银颗粒，确立了多达十条颗粒形貌随尺寸增大的演化路径，揭示了对称性失配引起的内在应力同表面能之间的竞争是此过程的主导机制；获得了银晶体颗粒形貌可控生长的方法，并获得了外形完美五次对称银颗粒，尺度达15微米，此为目前国际上报道的最大值，我们认为这也是机理允许的上限。形貌可控大尺寸金属颗粒生长方法对于金属催化剂制备和等离激元研究具有重要的意义。在利用脉冲电子束蒸发生长ZrW2O8薄膜以研究多原子基元取向不规则在表现热缩冷胀中的作用方面，未能取得令人信服的结果，表明此前申请中对此问题的认识不足。上述结果在未来的电子学和等离激元光学方面能找到应用。基于本课题研究结果在国际重要刊物上发表研究论文5篇，做了一些相关内容的科普及课程讲授，毕业博士2人且皆转入凝聚态物理博士后研究。申请人在课题执行期间还完成专著两部。