Solid state physics
The solid-state physics deals with the physics of matter in the solid state of aggregation . Crystalline solids are of particular importance . These are those that have a translational symmetry (periodic) structure, since this translational symmetry drastically simplifies the physical treatment of many phenomena or makes it possible in the first place. For this reason, the model of the ideal crystal lattice is often used even when the periodicity condition is only met to a very limited extent, for example only very locally. The deviation from the strict periodicity is then taken into account through corrections.
Appearances of solids
The physics of crystalline solids (crystal physics ) deals with solids that have a periodic structure.
- The crystal structure represents the static periodic order in the crystalline solid.
- The lattice vibrations describe the dynamics in the crystalline order. Their description often uses the quasiparticle model . In the case of lattice excitations, these are called phonons .
- The properties that go back to the electron shell of the regularly arranged atoms lead to a ribbon model and ribbon structure , the parameters of which make various macroscopic properties ( optics , etc.) calculable.
- The magnetic order represents the static order of the magnetic moments in the solid ( diamagnetism , paramagnetism , ferromagnetism , antiferromagnetism , spin density waves , magneto-optics, etc.).
- The magnetic excitations describe the dynamics of the magnetic order. The associated quasiparticles are called magnons .
Partly crystalline substance
Interface physics deals with the special features of interfaces, while surface physics is a special case of interface physics at interfaces with a vacuum . The physical properties of the few atomic layers near the interface differ due to the non-periodic boundary conditions from the physics inside, which is also called volume solid .
States of order in solids
When describing the regularity in the structure of the solid, one considers on the one hand the short-range order in the range of a few nanometers and on the other hand the long-range order, which relates to far greater distances.
|Status||Range of order||example|
|amorphous (local order)||next and next but one particle||Glass|
|monocrystalline (long-range order)||centimeter||monocrystalline ingots|
Subject areas of modern research
Investigation methods in solid state physics
In solid-state physics, similar to solid-state chemistry , a number of methods are used to investigate the properties of functional materials in particular and to understand their properties in the depth of the structure. This is important in many modern applications, such as electronics , computer chips , semiconductor technology , solar cells , batteries , lighting , metals , insulators . The important methods include:
The X-ray diffraction utilizes the effect of the diffraction of X-rays at crystal lattices to study the symmetry properties of solids, in 230 different so-called space groups are present. For this purpose X-ray diffractometer used. Materials can also be examined for their quality and purity as well as the crystallite size.
The neutron diffraction uses the same diffraction effect with the same basic principles as the X-ray diffraction, however, instead of X-rays neutrons used mostly in research nuclear reactors are provided. Due to the different wave properties of the massive neutron compared to the X-rays, the diffractometers are very large, usually several meters. In addition to the 230 space groups, it is particularly possible to study magnetic orders in crystals. With the addition of the spin , the magnetic space groups expand to 1651.
With magnetometers in particular the magnetic properties are examined. One of the common methods is the SQUID in conjunction with cryostats to determine the different types of magnetism and to identify the magnetic phase diagrams .
With tracer diffusion , the diffusion of atoms and ions in crystals is investigated. This is important in doping processes or for the temperature stability of materials, e.g. B. in the solid oxide fuel cell .
While the previous methods measure macroscopic properties, the methods of nuclear solid-state physics can be used to investigate local structures at the atomic level by using atomic nuclei as a probe. This z. B. the size of the magnetic field can be measured at the location of the core or local defects in the crystal lattice. Another important parameter are electrical field gradients , with which the local structure and its change with temperature changes or changes in the concentration of certain components in the material are researched. Measurement methods are e.g. B. Mössbauer spectroscopy , disturbed gamma-gamma angle correlation , nuclear magnetic resonance spectroscopy or muon spin spectroscopy .
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