Asymmetric Unit. The smallest unique fraction of a crystal structure. By applying the symmetry operations of the crystal's space group to the asymmetric unit, the complete unit cell is generated.
B
BVS. Bond Valence Sum. An empirical method in crystallography and coordination chemistry used to estimate the oxidation states of atoms based on observed bond lengths. shapeXT supports numerical approaches by Brown (1985) and O'Keeffe (1991), as well as calculations utilizing tabulated reference parameters (as provided on the IUCr website).
C
CShM. Continuous Shape Measures. A quantitative approach used in coordination chemistry to evaluate the degree of distortion of a molecule's coordination sphere relative to an ideal reference polyhedron (such as a perfect tetrahedron or octahedron). A CShM value of zero indicates a perfect match to the ideal shape. shapeXT provides an integrated tool to calculate and analyze these measures interactively.
COD. Crystallography Open Database. An open-access collection of crystal structures of organic, inorganic, metal-organic compounds, and minerals. shapeXT allows users to fetch and visualize structures directly from this database using a 7-digit ID.
CPU. Central Processing Unit. The primary hardware component responsible for executing general-purpose instructions and logic.
F
FXAA. Fast Approximate Anti-Aliasing. An efficient post-processing anti-aliasing technique that smooths edges across the rendered image without requiring additional VRAM or extra geometric sampling.
G
GPU. Graphics Processing Unit. A highly parallel hardware accelerator designed to perform thousands of mathematical calculations simultaneously. The GPU is optimized for massive parallel computing and shapeXT relies heavily on the GPU via Vulkan to execute shaders.
L
Laue class. One of the 11 centrosymmetric crystallographic point groups that describe the diffraction symmetry of a crystal. Because of Friedel's Law, standard X-ray diffraction patterns inherently exhibit a center of inversion. Therefore, the symmetry of a diffraction pattern always falls into one of the Laue classes, regardless of whether the actual crystal structure is centrosymmetric or not.
M
MoltenVK. A software translation layer that maps Vulkan API calls to Apple's Metal graphics framework. shapeXT relies on MoltenVK to bring its Vulkan renderer seamlessly to macOS and Apple Silicon hardware.
MSAA. Multi-Sample Anti-Aliasing. A hardware-accelerated anti-aliasing technique that improves edge quality by taking multiple samples per pixel along geometry boundaries. While it delivers crisp visuals, it significantly increases VRAM consumption especially at high screen resolutions.
O
OIT. Order-Independent Transparency. A technique that correctly renders overlapping transparent geometry (such as semi-transparent polyhedra) without requiring objects to be sorted from back-to-front. shapeXT utilizes a dedicated alpha buffer in GPU memory to achieve accurate real-time OIT.
S
Space Group. A mathematical description of the complete 3D symmetry of a crystal lattice. It combines point group symmetries (e.g., rotations and reflections) with translational symmetries (e.g., glide planes and screw axes). There are 230 unique space groups in three-dimensional crystallography. shapeXT fully supports all these 230 space groups.
SPIR-V. Standardized intermediate binary representation for graphics shaders. In shapeXT, all rendering shaders are compiled into SPIR-V to ensure minimal initialization times and cross-platform reliability. SPIR-V™ is a registered trademark of the Khronos Group Inc.
U
Unit Cell. The smallest repeating basic building block of a crystal lattice that represents the full symmetry and structural characteristics of the macroscopic crystal. It is defined by its lattice parameters: three lengths (a, b, c) and three angles (α, β, γ). By translating the unit cell along its axes, the entire crystal lattice is built.
V
VRAM. Video Random-Access Memory. High-speed memory physically located on the graphics card (GPU). It holds framebuffers, render targets, textures, and transparency buffers required to render 3D scenes.
VSA. Visible Solid Angle. A metric used to quantify the steric accessibility of a metal binding site and its capacity to accommodate additional ligands. By evaluating the open space around a central atom, this approach helps predict crossover points for coordination (e.g., binding in complex cations). shapeXT features integrated visible solid angle calculation and visualization.
Vulkan. Vulkan® is a new-generation graphics and compute API for high-efficiency, cross-platform access to GPUs. Vulkan and the Vulkan logo are registered trademarks of the Khronos Group Inc.