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Mr Yizheng Zhou

Yizheng

Research Student

Email: yizheng.zhou@qmul.ac.uk
Room Number: G. O. Jones Building, Room

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1st Supervisor: Dr. Martin Dove
2nd Supervisor: Dr. Andy Bushby

Project Title: Understanding Pressure Induced-Softening
Project Description:

As we know, most materials in our life always get big- ger when their temperature get higher. But there are some different materials which have counter-property, like ice. So we imagine if some materials which have the same property like ice exist, and why they have these property, negative thermal expansion(NTE) property. In the middle of the last century, the possibility of NTE was discussed, the decisive parametre of thermal expan- sion, gruneisen constant may be negative, this will be discussed in next section. Time to about last ten years of 20th century, NTE materilas start to be found. At start, only very few materials, such as ZrW2 O8 and LiAlSiO4 , were found NTE property in a very limited range of tem- perature. Afterwards, there are a few series of materials been found, some of them follow previous discovery, such as ZrV2−x Px O7 . In additional, some simple oxides, such as Cu2O, were found that they also have NTE property, and their similar structure materials which the oxygen anion is replaced by an molecular ion or ligand maybe also have NTE propery, such as ScF3.

In recent years, people try to use both experimental and theoretical method to make the mechanisms of NTE clearer. Some of works show some NTE materials have pressure-induced softening property, such as Zn(CN)2 and amorphous silica. For Zn(CN)2, it has shown NTE using ueutron powder diffraction and molecular dynamics simulations. And Martin’s previous work on amorphous silica based on experiment data showing strange pressure effects beacause of fluctuations. So I try to build a simple fluctuatal model to give a new insight into the mechanism of this property.

 

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