Overview of the Experimental Findings

As summarized in the previous sections, the development of a reliable methodology to build and study realistic binary chalcogenides has been a stepwize process. After solving the main issues related to the FSDP and the IRO, it is natural to focus on exploring the phase diagram of these disordered materials. Indeed the modifications of the structural and the elecfionic properties of these systems under high pressure and/or temperature are of particular interest. 

Experimentally, the crystallization and the amorphization of binary amorphous systems under pressure have already been the subjects of many studies [73-81]. In 1965, Prewitt and Young [73] found two new crystalline phases of Germanium and Silicium disulfides at T=300 K under pressure. Later, Shimada and Dachille [74] studied the crystallization of amorphous GeSe2 under pressure and found that three different crystalline phases exist depending on temperature and pressure. They also quoted that the crystallization was inhibited for temperatures lower than T=573 K. 

In contrast with the work by Shimada [74] Grande and Co. [76] observed that amorphous GeSe2 at T= 250 - 300 °C partly crystallized in two phases when compressed, the first at 3.0 GPa and the second at 7.7GPa. Also, during quenching performed at 7.7 GPa an orthorhombic polymorph of GeSc2 was found at 500 C. 

In further work the same team [82] used angle-dispersive X-ray diffraction in the pressure range 2-6 GPa to study crystalline GeSc2. This confirmed the transition to a three-dimensional crystalline structure above 2 GPa at 698 K. This transition was explained by an anisotropic lattice distortion due to the cooperative tilting of rigid Ge(Sc4) tetrahedra. The authors claimed that a similar transition, including anomalous compressibility and thermal expansion phenomena, could be observed in 

The GeSe2 system has also been the subject of X-ray diffraction study under pressure in the liquid phase [77]. It was found that under compression the connectivity of the liquid changes from a 2D to 3D. The 2D structure is characterized by a mixture of ES and CS tetrahedra, while the 3D one is only made by CS tetrahedra. This conversion from a mixture of ES/CS to a full CS network is accompanied by a breakdown of the IRO, completely lost above 2.5 GPa. 

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We will first present an overview of the experimental findings in terms of structure diagrams temperature versus wax volume fraction maps that indicate the different structures found by SANS experiments for each of the investigated polymer-wax systems. This overview will be then followed by a detailed presentation of the structures and morphologies formed by the... 

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