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  2. Phase problem - Wikipedia

    en.wikipedia.org/wiki/Phase_problem

    In physics, the phase problem is the problem of loss of information concerning the phase that can occur when making a physical measurement. The name comes from the field of X-ray crystallography , where the phase problem has to be solved for the determination of a structure from diffraction data. [ 1 ]

  3. Stefan problem - Wikipedia

    en.wikipedia.org/wiki/Stefan_problem

    This is accomplished by solving heat equations in both regions, subject to given boundary and initial conditions. At the interface between the phases (in the classical problem) the temperature is set to the phase change temperature. To close the mathematical system a further equation, the Stefan condition, is required. This is an energy balance ...

  4. Patterson function - Wikipedia

    en.wikipedia.org/wiki/Patterson_function

    The Patterson function is used to solve the phase problem in X-ray crystallography. It was introduced in 1935 by Arthur Lindo Patterson while he was a visiting researcher in the laboratory of Bertram Eugene Warren at MIT. [1] [2] The Patterson function is defined as

  5. Direct methods (crystallography) - Wikipedia

    en.wikipedia.org/wiki/Direct_methods...

    In crystallography, direct methods are a family of methods for estimating the phases of the Fourier transform of the scattering density from the corresponding magnitudes. . The methods generally exploit constraints or statistical correlations between the phases of different Fourier components that result from the fact that the scattering density must be a positive real nu

  6. Molecular replacement - Wikipedia

    en.wikipedia.org/wiki/Molecular_replacement

    Molecular replacement (MR) [1] is a method of solving the phase problem in X-ray crystallography.MR relies upon the existence of a previously solved protein structure which is similar to our unknown structure from which the diffraction data is derived.

  7. Phase diagram - Wikipedia

    en.wikipedia.org/wiki/Phase_diagram

    The phase diagram shows, in pressure–temperature space, the lines of equilibrium or phase boundaries between the three phases of solid, liquid, and gas. The curves on the phase diagram show the points where the free energy (and other derived properties) becomes non-analytic: their derivatives with respect to the coordinates (temperature and ...

  8. Phase-field model - Wikipedia

    en.wikipedia.org/wiki/Phase-field_model

    Phase-field models are usually constructed in order to reproduce a given interfacial dynamics. For instance, in solidification problems the front dynamics is given by a diffusion equation for either concentration or temperature in the bulk and some boundary conditions at the interface (a local equilibrium condition and a conservation law), [14] which constitutes the sharp interface model.

  9. CALPHAD - Wikipedia

    en.wikipedia.org/wiki/CALPHAD

    CALPHAD stands for Computer Coupling of Phase Diagrams and Thermochemistry, a methodology introduced in 1970 by Larry Kaufman, originally known as CALculation of PHAse Diagrams. [1] [2] [3] An equilibrium phase diagram is usually a diagram with axes for temperature and composition of a chemical system. It shows the regions where substances or ...