From 8572384954e0389af3466d6b27296e5891e54734 Mon Sep 17 00:00:00 2001 From: Rolf Stierle Date: Fri, 20 Feb 2026 17:16:09 +0100 Subject: [PATCH 1/2] Fix isothermal compressibility calculation Comment includes negative sign, calculation doesn't. Results in negative values for the calculation of isothermal_compressibility(). --- crates/feos-core/src/state/residual_properties.rs | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/crates/feos-core/src/state/residual_properties.rs b/crates/feos-core/src/state/residual_properties.rs index 179ff6d19..554facf08 100644 --- a/crates/feos-core/src/state/residual_properties.rs +++ b/crates/feos-core/src/state/residual_properties.rs @@ -272,7 +272,7 @@ where /// Isothermal compressibility: $\kappa_T=-\frac{1}{V}\left(\frac{\partial V}{\partial p}\right)_{T,N_i}$ pub fn isothermal_compressibility(&self) -> InvP { - (self.dp_dv(Contributions::Total) * self.volume).inv() + -(self.dp_dv(Contributions::Total) * self.volume).inv() } // entropy derivatives From e74cfd72e029638cd20fff0281680418583ac00c Mon Sep 17 00:00:00 2001 From: Rolf Stierle Date: Fri, 20 Feb 2026 17:25:56 +0100 Subject: [PATCH 2/2] CHANGELOG updated --- CHANGELOG.md | 1 + 1 file changed, 1 insertion(+) diff --git a/CHANGELOG.md b/CHANGELOG.md index d233d0196..c198c525f 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0 ## [Unreleased] ### Changed - Automatically detect VLLEs in `BinaryPhaseDiagram`. [#341](https://github.com/feos-org/feos/pull/341) +- Correct missing minus sign for `isothermal_compressibility`. [#342](https://github.com/feos-org/feos/pull/342) ## [0.9.3] - 2026-01-26 ### Added