Structure of materials

This week there will be an introduction into the overall content of the class. We will introduce the structure of materials on examples, go through a reminder on atoms and bond, and get started with crystallography: The hard sphere model

This week we will continue with the description of crystals and introduce lattice and motif. We will consider the cubic crystal system and look at primitive and conventional unit cells. We will discuss coordination and interstitial sites, discuss some typical crystals formed by metals, ionic crystals and covalent crystals.

This week we will discuss symmetry in crystallography. We will look at Bravais lattice, symmetry operations, point groups and how it is used to built up the 2D plane groups and extend it to 3D space groups.

We will introduce the mathematical description of crystals, the Miller indices. With some reminders to basic Euclidian geometry we will see how to work with crystal directions and crystal planes. We will see that it is importance to know symmetry of the crystal system.

lecture and exercise cancelled

We will introduce the reciprocal lattice, discuss how this helps to calculate distances between crystallographic planes and its relation to diffraction. We will introduce Bragg's law and Laue's condition and look at diffraction as the fourier transform of the investigated crystal

This week we will look at Diffraction as Fourier transform of a crystal and what that means for structure determination. After we have seen last week how the reciprocal space lattice (and Bragg's Law and Laue's condition) will give us the location of diffraction spot, we will look at the intensity variation introduced by the motif, discussing the atomic form factor and the unit cell structure factor. This will lead us to explain systematic absences of diffraction peak.

We will look at diffraction from an experimental point of view. What main measurements method exists for different sample types, such as single crystals, and polycrystals with preferred orientation (textured materials) or random orientation (powder samples). We will repeat in the framework of diffraction different parts of the crystallography lectures so far, including the view of crystals as closed packed spheres, crystal planes and Miller indicies as well as crystal symmetry.

This week we will start discussing the structure of amorphous materials, glasses. We will look into what long- and short-range order means, look at some average structure parameters commonly used and introdue the pair distribution function. We will also look at structural models for different types of glasses.

This week we will look at polymers and how their structure can be described. We will discuss the random-coil model and the adapations to it due to interactions within the chain itself or its surrounding. We will also discuss semi-crystallinity and some common feature of crystal structure of polymers. While focusing on structure we will also look what implication on mechanical properties can be expected.

This week we will look at scattering at smaller scattering angles compared to diffraction we looked at so far, thus we can probe structures in the nanoscale. We will look how the scattering curves depend on size, shape and arrangement and the basics of how it can be analyzed.

We will look into the main components found in biological materials and discuss main aspects of their structures. We will relate how polymeric molcules such as DNA and protein do not follow the random walk model but take more controlled structural forms. If time allows, we will start discussing hybrid/composite structures.

This week we will finish with hybrid and composite material lecture and repeat some of the key contents of this course. The exercise (apart from finishing the exercise distributed in week 12 on hybrid materials) als additional exam questions from last years exam.