The lattice is usually distorted near impurities, crystal defects, and the crystal's surface. These parameters typically depend on the temperature, pressure (or, more generally, the local state of mechanical stress within the crystal), electric and magnetic fields, and its isotopic composition. The angles α, β, and γ are usually specified in degrees.Ī chemical substance in the solid state may form crystals in which the atoms, molecules, or ions are arranged in space according to one of a small finite number of possible crystal systems (lattice types), each with fairly well defined set of lattice parameters that are characteristic of the substance. Their SI unit is the meter, and they are traditionally specified in angstroms (Å) an angstrom being 0.1 nanometer (nm), or 100 picometres (pm). The three numbers represent the size of the unit cell, that is, the distance from a given atom to an identical atom in the same position and orientation in a neighboring cell (except for very simple crystal structures, this will not necessarily be disance to the nearest neighbor). The crystal lattice parameters a, b, and c have the dimension of length. A simple cubic crystal has only one lattice constant, the distance between atoms, but in general lattices in three dimensions have six lattice constants: the lengths a, b, and c of the three cell edges meeting at a vertex, and the angles α, β, and γ between those edges. SingleCrystal provides simulation of key diffraction techniques – Laue, Precession & transmission electron diffraction – with control over sample and instrumental parameters.Unit cell definition using parallelepiped with lengths a, b, c and angles between the sides given by α, β, γ Ī lattice constant or lattice parameter is one of the physical dimensions and angles that determine the geometry of the unit cells in a crystal lattice, and is proportional to the distance between atoms in the crystal. Reciprocal lattice sections can also be visualized, with control over layer height. SingleCrystal 3’s multi-core architecture dramatically accelerates simulation times for massive structures such as proteins. Once the intensity calculation is complete, diffraction patterns can be rotated in real time using the mouse or multi-touch gestures on the trackpad. SingleCrystal can label reflexions, show systematic absences, and lets you measure distances and angles between diffraction spots. You can colour-code your patterns by intensity, wavelength, or even phase angle. Diffraction- and structural data can be browsed and sorted on screen. You can edit lattice parameters and site occupancies – and opt to exclude certain sites from the diffraction calculation. SingleCrystal lets you rotate your (virtual) crystal in real time, using multi-touch gestures (Mac), by clicking-and-dragging with the mouse, clicking toolbar “tilt” controls, or using the keyboard. Precise tilts can be entered, or you can define a view direction as a plane normal or lattice vector. Other controls allow you to change the scale (camera constant), saturation, sample thickness, wavelength and other parameters. ![]() You can use SingleCrystal as a virtual lightbox: just drag-and-drop a diffraction image into any window, zoom in to examine fine details, move or rotate the image. Use the translucent Ruler, Protractor and Grid overlays to measure your pattern and copy the results to the clipboard. Simulated patterns can be superimposed above observed patterns, for direct comparison. With the Grid tool, auto-indexing is a breeze: just position the grid points over your observed pattern (TEM or Precession photos) and let SingleCrystal calculate the best-fit orientation and index your diffraction spots. To help you navigate through diffraction space, you can take advantage of a live stereographic projection (“stereogram”) which can be displayed on the right-hand side of each diffraction window. The stereogram shows the angular positions of plane normals or lattice vectors (zone axes) plotted as poles and optionally as great circle traces – and is fully customizable.
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