Thermodynamic integration

Thermodynamic integration is used to calculate the difference in the Helmholtz energy function between two states. The path must be continuous and reversible. One has a continuously variable energy function $U_{\lambda }$ such that Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \lambda=0} , Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle U_\lambda=U_0} and Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \lambda=1} , Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle U_\lambda=U}

$\Delta A=A-A_{0}=\int _{0}^{1}d\lambda \left\langle {\frac {\partial U_{\lambda }}{\partial \lambda }}\right\rangle _{\lambda }$

where

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \left.U_\lambda\right.=(1-\lambda)U_0 + \lambda U} .

See also

• Gibbs-Duhem integration