Rapid prototyping of flexible crystal models
Tan, Malcolm Yong Liang.
Date of Issue2009
School of Mechanical and Aerospace Engineering
Crystalline minerals have many interesting properties, and many of these properties have useful applications. By studying the minerals’ crystal structures, their properties and behaviors, can be better understood and appreciated. ‘Balls-and-sticks’ is the very common method used for representing minerals’ crystallographic data. In this project, the crystal structures are to be made ‘flexible’ to imitate certain crystal behaviors, such as polymorphism of silica (SiO2) – one example is the transformation of alpha quartz (at room temperatures and pressures) to beta quartz (at elevated temperatures and pressures), and vice versa. In order to do this, spheres representing the supposedly ‘flexible’ atoms are replaced by spherical/ball joints to induce this flexibility. Two possible approaches exist as to fabrication. The conventional approach involves fabrication using balls-and-sticks. However, this is often too time-consuming, as well as lost of crystallographic accuracy when the structures become larger and more complex. Therefore, rapid-prototyping is chosen to fabricate these crystal structures more efficiently and accurately. In order for the crystal to be rapid-prototyped, a mineral’s crystallographic data is first obtained (as a CIF file), and then opened by a Java-based viewer Jmol. Jmol is a software which permits viewing of crystal structures in real-time 3D. Manipulation such as the displaying n numbers of unit cells to control the size of the crystal structure is possible in Jmol – and upon obtaining the desirable crystal structure (such as structure size, bond size, etc), a ‘snapshot’ of the crystal structure can be captured, and the information is exported to files. These intermediate files are read by an AutoCAD macro, programmed by the author, to replicate the crystal model in the CAD environment. Post-processing is done to ensure the CAD model is fit for fabrication, before it is exported as a stereo-lithography file (STL file) to the rapid-prototyping machine for fabrication. What will ultimately result is an accurate product: a flexible ball-and-stick representation of the crystal structure.
Final Year Project (FYP)
Nanyang Technological University