athermal solution

An athermal solution is a type of mixture where, upon combining components, there is no net absorption or release of heat. This means the enthalpy of mixing is zero ((H^E = 0)). In such solutions, the excess Gibbs energy ((G^E)) is solely determined by the excess entropy ((S^E)), which reflects the change in disorder when the components are mixed.1

Athermal solutions are distinct from regular solutions, where the excess entropy is zero ((S^E = 0)) but the excess enthalpy is not. Real solutions are typically neither purely regular nor athermal, representing a combination of both behaviors. The concept is particularly relevant when dealing with mixtures involving large molecules, such as polymers, where the flexibility and arrangement of these molecules significantly impact the solution's entropy.21