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  2. Wigner–Seitz radius - Wikipedia

    en.wikipedia.org/wiki/Wigner–Seitz_radius

    The Wigner–Seitz radius, named after Eugene Wigner and Frederick Seitz, is the radius of a sphere whose volume is equal to the mean volume per atom in a solid (for first group metals). [1] In the more general case of metals having more valence electrons, r s {\displaystyle r_{\rm {s}}} is the radius of a sphere whose volume is equal to the ...

  3. Close-packing of equal spheres - Wikipedia

    en.wikipedia.org/wiki/Close-packing_of_equal_spheres

    The distance between the centers along the shortest path namely that straight line will therefore be r 1 + r 2 where r 1 is the radius of the first sphere and r 2 is the radius of the second. In close packing all of the spheres share a common radius, r. Therefore, two centers would simply have a distance 2r.

  4. Sphere - Wikipedia

    en.wikipedia.org/wiki/Sphere

    S ‍ 1: a 1-sphere is a circle of radius r; S ‍ 2: a 2-sphere is an ordinary sphere; S ‍ 3: a 3-sphere is a sphere in 4-dimensional Euclidean space. Spheres for n > 2 are sometimes called hyperspheres. The n-sphere of unit radius centered at the origin is denoted S ‍ n and is often referred to as "the" n-sphere. The ordinary sphere is a ...

  5. Circle packing - Wikipedia

    en.wikipedia.org/wiki/Circle_packing

    While the circle has a relatively low maximum packing density, it does not have the lowest possible, even among centrally-symmetric convex shapes: the smoothed octagon has a packing density of about 0.902414, the smallest known for centrally-symmetric convex shapes and conjectured to be the smallest possible. [3]

  6. Spherical coordinate system - Wikipedia

    en.wikipedia.org/wiki/Spherical_coordinate_system

    For example, one sphere that is described in Cartesian coordinates with the equation x 2 + y 2 + z 2 = c 2 can be described in spherical coordinates by the simple equation r = c. (In this system—shown here in the mathematics convention—the sphere is adapted as a unit sphere, where the radius is set to unity and then can generally be ignored ...

  7. Contact mechanics - Wikipedia

    en.wikipedia.org/wiki/Contact_mechanics

    An elastic sphere of radius indents an elastic half-space where total deformation is , causing a contact area of radius a = R d {\displaystyle a={\sqrt {Rd}}} The applied force F {\displaystyle F} is related to the displacement d {\displaystyle d} by [ 4 ]

  8. Surface area - Wikipedia

    en.wikipedia.org/wiki/Surface_area

    A sphere of radius r has surface area 4πr 2.. The surface area (symbol A) of a solid object is a measure of the total area that the surface of the object occupies. [1] The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc length of one-dimensional curves, or of the surface area for polyhedra (i.e., objects with ...

  9. Stokes' law - Wikipedia

    en.wikipedia.org/wiki/Stokes'_law

    For the case of a sphere in a uniform far field flow, it is advantageous to use a cylindrical coordinate system (r, φ, z). The z –axis is through the centre of the sphere and aligned with the mean flow direction, while r is the radius as measured perpendicular to the z –axis. The origin is at the sphere centre.