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  2. Order of approximation - Wikipedia

    en.wikipedia.org/wiki/Order_of_approximation

    In the zeroth-order example above, the quantity "a few" was given, but in the first-order example, the number "4" is given. A first-order approximation of a function (that is, mathematically determining a formula to fit multiple data points) will be a linear approximation, straight line with a slope: a polynomial of degree 1.

  3. Rate equation - Wikipedia

    en.wikipedia.org/wiki/Rate_equation

    In chemistry, the rate equation (also known as the rate law or empirical differential rate equation) is an empirical differential mathematical expression for the reaction rate of a given reaction in terms of concentrations of chemical species and constant parameters (normally rate coefficients and partial orders of reaction) only. [1]

  4. Kubo formula - Wikipedia

    en.wikipedia.org/wiki/Kubo_formula

    The Kubo formula, named for Ryogo Kubo who first presented the formula in 1957, [1] [2] is an equation which expresses the linear response of an observable quantity due to a time-dependent perturbation.

  5. Finite difference method - Wikipedia

    en.wikipedia.org/wiki/Finite_difference_method

    For example, consider the ordinary differential equation ′ = + The Euler method for solving this equation uses the finite difference quotient (+) ′ to approximate the differential equation by first substituting it for u'(x) then applying a little algebra (multiplying both sides by h, and then adding u(x) to both sides) to get (+) + (() +).

  6. Zeroth-order - Wikipedia

    en.wikipedia.org/wiki/Zeroth-order

    Download as PDF; Printable version; In other projects ... move to sidebar hide. Zeroth-order may refer to: Zeroth-order approximation, a rough approximation; Zeroth ...

  7. Zeroth order approximation - Wikipedia

    en.wikipedia.org/?title=Zeroth_order...

    Download as PDF; Printable version; In other projects Appearance. ... Redirect page. Redirect to: Order of approximation#Zeroth-order; Retrieved from "https: ...

  8. Zero order - Wikipedia

    en.wikipedia.org/wiki/Zero_order

    Zero order reaction. Zero-order process (statistics), a sequence of random variables, each independent of the previous ones; Zero order process (chemistry), a chemical reaction in which the rate of change of concentration is independent of the concentrations; Zeroth-order approximation, an approximation of a function by a constant

  9. Perturbation theory - Wikipedia

    en.wikipedia.org/wiki/Perturbation_theory

    The zero-order energy is the sum of orbital energies. The first-order energy is the Hartree–Fock energy and electron correlation is included at second-order or higher. Calculations to second, third or fourth order are very common and the code is included in most ab initio quantum chemistry programs.