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The Gibbs–Helmholtz equation is a thermodynamic equation used to calculate changes in the Gibbs free energy of a system as a function of temperature. It was originally presented in an 1882 paper entitled " Die Thermodynamik chemischer Vorgänge " by Hermann von Helmholtz .
The Helmholtz equation has a variety of applications in physics and other sciences, including the wave equation, the diffusion equation, and the Schrödinger equation for a free particle. In optics, the Helmholtz equation is the wave equation for the electric field. [1] The equation is named after Hermann von Helmholtz, who studied it in 1860. [2]
In contrast, the Gibbs free energy or free enthalpy is most commonly used as a measure of thermodynamic potential (especially in chemistry) when it is convenient for applications that occur at constant pressure. For example, in explosives research Helmholtz free energy is often used, since explosive reactions by their nature induce pressure ...
In thermodynamics, the Gibbs free energy (or Gibbs energy as the recommended name; symbol ) is a thermodynamic potential that can be used to calculate the maximum amount of work, other than pressure–volume work, that may be performed by a thermodynamically closed system at constant temperature and pressure.
The equations below (in terms of free energy) may be restated in terms of the canonical partition function by simple mathematical manipulations. Historically, the canonical ensemble was first described by Boltzmann (who called it a holode) in 1884 in a relatively unknown paper. [2] It was later reformulated and extensively investigated by Gibbs ...
The Gibbs−Duhem equation applies to homogeneous thermodynamic systems. It does not apply to inhomogeneous systems such as small thermodynamic systems, [2] systems subject to long-range forces like electricity and gravity, [3] [4] or to fluids in porous media. [5] The equation is named after Josiah Willard Gibbs and Pierre Duhem.
Antoine equation; Bejan number; Bowen ratio; Bridgman's equations; Clausius–Clapeyron relation; Departure functions; Duhem–Margules equation; Ehrenfest equations; Gibbs–Helmholtz equation; Phase rule; Kopp's law; Noro–Frenkel law of corresponding states; Onsager reciprocal relations; Stefan number; Thermodynamics; Timeline of ...
The differential form of Helmholtz free energy is = = (), = From symmetry of second derivatives = and therefore that = The other two Maxwell relations can be derived from differential form of enthalpy = + and the differential form of Gibbs free energy = in a similar way.