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  2. Sigma-pi and equivalent-orbital models - Wikipedia

    en.wikipedia.org/wiki/Sigma-pi_and_equivalent...

    The σ-π model differentiates bonds and lone pairs of σ symmetry from those of π symmetry, while the equivalent-orbital model hybridizes them. The σ-π treatment takes into account molecular symmetry and is better suited to interpretation of aromatic molecules ( Hückel's rule ), although computational calculations of certain molecules tend ...

  3. Pi bond - Wikipedia

    en.wikipedia.org/wiki/Pi_bond

    Two pi bonds are the maximum that can exist between a given pair of atoms. Quadruple bonds are extremely rare and can be formed only between transition metal atoms, and consist of one sigma bond, two pi bonds and one delta bond. A pi bond is weaker than a sigma bond, but the combination of pi and sigma bond is stronger than either bond by itself.

  4. List of formulae involving π - Wikipedia

    en.wikipedia.org/wiki/List_of_formulae_involving_π

    More formulas of this nature can be given, as explained by Ramanujan's theory of elliptic functions to alternative bases. Perhaps the most notable hypergeometric inversions are the following two examples, involving the Ramanujan tau function τ {\displaystyle \tau } and the Fourier coefficients j {\displaystyle \mathrm {j} } of the J-invariant ...

  5. Sigma bond - Wikipedia

    en.wikipedia.org/wiki/Sigma_bond

    In chemistry, sigma bonds (σ bonds) or sigma overlap are the strongest type of covalent chemical bond. [1] They are formed by head-on overlapping between atomic orbitals along the internuclear axis. Sigma bonding is most simply defined for diatomic molecules using the language and tools of symmetry groups. In this formal approach, a σ-bond is ...

  6. Leibniz formula for π - Wikipedia

    en.wikipedia.org/wiki/Leibniz_formula_for_π

    The formula is a special case of the Euler–Boole summation formula for alternating series, providing yet another example of a convergence acceleration technique that can be applied to the Leibniz series. In 1992, Jonathan Borwein and Mark Limber used the first thousand Euler numbers to calculate π to 5,263 decimal places with the Leibniz ...

  7. SigmaPlot - Wikipedia

    en.wikipedia.org/wiki/SigmaPlot

    SigmaPlot is a proprietary software package for scientific graphing and data analysis.It runs on Microsoft Windows. [1]The software can read multiple formats, such as Microsoft Excel spreadsheets, and can also perform mathematical transforms and statistical analyses.

  8. Symmetry number - Wikipedia

    en.wikipedia.org/wiki/Symmetry_number

    The symmetry number or symmetry order of an object is the number of different but indistinguishable (or equivalent) arrangements (or views) of the object, that is, it is the order of its symmetry group. The object can be a molecule, crystal lattice, lattice, tiling, or in general any kind of mathematical object that admits symmetries.

  9. Machin-like formula - Wikipedia

    en.wikipedia.org/wiki/Machin-like_formula

    Machin-like formulas for π can be constructed by finding a set of integers , =, where all the prime factorisations of ⁠ + ⁠, taken together, use a number of distinct primes , and then using either linear algebra or the LLL basis-reduction algorithm to construct linear combinations of arctangents of . For example, in the Størmer formula ...