Linking Micro-Structural Disorder To Dynamics And Abnormal Elasticity Of Amorphous Systems

We use various kinds of materials in our daily life.For crystalline materials,its mechanical properties could be well described by the theory of elastic mechanics,its mi-croscopic phenomenons could be explained by the quantum mechanics.Above atomic level,the aggregation behavior could be described by classic mechanics,solid state physics,statistic mechanics.However,there exits a lot of amorphous materials such as glass,asphalt,sand piles,on which many studies have been done without a unified,effective research paradigm so far.Recently,with the rise of the development of the techniques of the micro-nano processing,there grows up a field of meta-materials de-sign.Compared with the classic materials,basic constructions of meta-materials are designed artificially with the scale larger than atomic scale.Meta-materials are also ap-pealing in the fact that there are various properties for the meta-materials which classic materials do not have.The research of this thesis concentrates on the influence of the amorphous disorder on the dynamics of the system,as well as of the mechanical properties on the materials.With these researches as a guide,we also develop the technique to design a negative-Poisson-ratio materials by increasing the extent of amorphous order.In the first chapter,we introduce the background of this thesis.Firstly,we will in-troduce two related amorphous research fields,i.e.,the glass transition and the Jamming transition.Glass is a typical amorphous system.It will skip crystallization and will be more viscous so as to become a solid when researcher decreases the temperature.This is a process that is clearly different from the traditional phase transition.Jamming tran-sition originates from the random closed packing of the granular systems.Secondly,we will introduce the mate-materials,especially the field of negative-Poisson-ratio meta-materials.In the second chapter,we will discuss the amorphous systems and briefly introduce elastic mechanics.We will firstly conclude the theory of the elastic mechanics,and then its application in the amorphous systems.Thirdly we will introduce some researches of the amorphous in the point of the view of the elastic theory.In the third chapter we will concentrate on our main research.That is,we de-sign and implement the negative-Poisson-ratio systems by introducing various kinds of randomness,on the basis of the spring-network systems.We notice that we can anoma-lously alternate bulk modulus and shear modulus of the system by introducing specific kind of randomness on the spring network of the triangle lattice crystal at our previous research,and implement negative Poisson-ratio.By studying the connections between the attributes of the spring and its mechanic properties,we find out the significantly dif-ferent contributions of the lengths of springs on various modulus.And based on these findings,we develop more flexible and effective design for negative Poisson-ratio sys-tems.In the fourth chapter,we use an order parameter ? to study the spatial difference of restricted system dynamics.The ? is defined under the zero-temperature config-uration,and can be used to predict the motility of particles at low temperatures.We find that the spatial distribution of is correlated with that of the structural relaxation of supercooled liquids,when there exists fixed boundaries.This provides another evi-dence showing that the dynamics of supercooled liquids can be predicted by properties of zero-temperature states.We also find that the spatial distribution of ? satisfies a scaling relation,indicating the criticality of the jamming transition.In the fifth chapter,we will summarize the work of the thesis and look forward to the future work.