feos-org · prehner · Oct 17, 2025 · Oct 16, 2025 · Oct 16, 2025 · Oct 16, 2025
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
@@ -28,7 +28,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        model: [pcsaft, epcsaft, gc_pcsaft, pets, uvtheory, saftvrqmie, saftvrmie]
+        model: [pcsaft, epcsaft, gc_pcsaft, pets, uvtheory, saftvrqmie, saftvrmie, multiparameter]
 
     steps:
       - uses: actions/checkout@v4

diff --git a/crates/feos-core/src/equation_of_state/mod.rs b/crates/feos-core/src/equation_of_state/mod.rs
@@ -48,7 +48,7 @@ impl<I> EquationOfState<Vec<I>, NoResidual> {
     }
 }
 
-impl<I: Clone, R: ResidualDyn> ResidualDyn for EquationOfState<Vec<I>, R> {
+impl<I, R: ResidualDyn> ResidualDyn for EquationOfState<Vec<I>, R> {
     fn components(&self) -> usize {
         self.residual.components()
     }

diff --git a/crates/feos-core/src/state/mod.rs b/crates/feos-core/src/state/mod.rs
@@ -188,7 +188,7 @@ where
     }
 }
 
-impl<E: Residual, N: Dim, D: DualNum<f64> + Copy> fmt::Display for State<E, N, D>
+impl<E: Residual<N, D>, N: Dim, D: DualNum<f64> + Copy> fmt::Display for State<E, N, D>
 where
     DefaultAllocator: Allocator<N>,
 {

diff --git a/crates/feos/Cargo.toml b/crates/feos/Cargo.toml
@@ -19,6 +19,7 @@ petgraph = { workspace = true, optional = true }
 thiserror = { workspace = true }
 num-traits = { workspace = true }
 serde = { workspace = true }
+serde_json = { workspace = true }
 indexmap = { workspace = true }
 rayon = { workspace = true, optional = true }
 itertools = { workspace = true }
@@ -32,7 +33,6 @@ feos-dft = { workspace = true, optional = true }
 approx = { workspace = true }
 quantity = { workspace = true, features = ["approx"] }
 criterion = { workspace = true }
-serde_json = { workspace = true }
 
 [features]
 default = []
@@ -45,6 +45,7 @@ uvtheory = []
 pets = []
 saftvrqmie = []
 saftvrmie = ["association"]
+multiparameter = []
 rayon = ["dep:rayon", "ndarray/rayon", "feos-core/rayon", "feos-dft?/rayon"]
 all_models = [
     "dft",
@@ -55,6 +56,7 @@ all_models = [
     "pets",
     "saftvrqmie",
     "saftvrmie",
+    "multiparameter"
 ]
 
 [[bench]]

diff --git a/crates/feos/src/lib.rs b/crates/feos/src/lib.rs
@@ -46,6 +46,8 @@ pub mod hard_sphere;
 pub mod epcsaft;
 #[cfg(feature = "gc_pcsaft")]
 pub mod gc_pcsaft;
+#[cfg(feature = "multiparameter")]
+pub mod multiparameter;
 #[cfg(feature = "pcsaft")]
 pub mod pcsaft;
 #[cfg(feature = "pets")]

diff --git a/crates/feos/src/multiparameter/ideal_gas_function.rs b/crates/feos/src/multiparameter/ideal_gas_function.rs
@@ -0,0 +1,140 @@
+use num_dual::DualNum;
+use serde::Deserialize;
+use serde_json::Value;
+use std::collections::HashMap;
+
+#[derive(Clone, Deserialize)]
+pub struct IdealGasFunctionJson {
+    #[serde(rename = "type")]
+    pub ty: String,
+    #[serde(flatten)]
+    parameters: HashMap<String, Value>,
+}
+
+pub struct IdealGasFunctionIterator {
+    inner: IdealGasFunctionJson,
+    count: usize,
+    index: usize,
+}
+
+impl Iterator for IdealGasFunctionIterator {
+    type Item = IdealGasFunction;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.index == self.count {
+            return None;
+        }
+        let mut parameters: HashMap<_, _> = self
+            .inner
+            .parameters
+            .iter()
+            .map(|(k, v)| {
+                (
+                    k.clone(),
+                    if self.inner.ty == "IdealGasHelmholtzCP0AlyLee" {
+                        // AlyLee parameters are stored as list instead of named parameters
+                        v.clone()
+                    } else {
+                        v.as_array().map_or(v, |v| &v[self.index]).clone()
+                    },
+                )
+            })
+            .collect();
+        if self.inner.ty == "IdealGasHelmholtzCP0AlyLee" {
+            self.index += 5
+        } else {
+            self.index += 1;
+        }
+        parameters.insert("type".into(), serde_json::to_value(&self.inner.ty).unwrap());
+        Some(serde_json::from_value(serde_json::to_value(parameters).unwrap()).unwrap())
+    }
+}
+
+impl IntoIterator for IdealGasFunctionJson {
+    type Item = IdealGasFunction;
+    type IntoIter = IdealGasFunctionIterator;
+
+    fn into_iter(self) -> Self::IntoIter {
+        let count = self
+            .parameters
+            .values()
+            .map(|e| e.as_array().map_or(1, Vec::len))
+            .max()
+            .unwrap();
+        IdealGasFunctionIterator {
+            count,
+            inner: self,
+            index: 0,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Deserialize)]
+#[serde(tag = "type")]
+#[expect(non_snake_case)]
+pub enum IdealGasFunction {
+    IdealGasHelmholtzLead { a1: f64, a2: f64 },
+    IdealGasHelmholtzLogTau { a: f64 },
+    IdealGasHelmholtzPower { n: f64, t: f64 },
+    IdealGasHelmholtzPlanckEinstein { n: f64, t: f64 },
+    IdealGasHelmholtzPlanckEinsteinFunctionT { Tcrit: f64, n: f64, v: f64 },
+    IdealGasHelmholtzPlanckEinsteinGeneralized { c: f64, d: f64, n: f64, t: f64 },
+    IdealGasHelmholtzCP0AlyLee { T0: f64, Tc: f64, c: [f64; 5] },
+    IdealGasHelmholtzCP0Constant { T0: f64, Tc: f64, cp_over_R: f64 },
+    IdealGasHelmholtzCP0PolyT { T0: f64, Tc: f64, c: f64, t: f64 },
+    IdealGasHelmholtzEnthalpyEntropyOffset { a1: f64, a2: f64 },
+}
+
+impl IdealGasFunction {
+    pub fn evaluate<D: DualNum<f64> + Copy>(&self, delta: D, tau: D) -> D {
+        match *self {
+            IdealGasFunction::IdealGasHelmholtzLead { a1, a2 } => delta.ln() + a1 + tau * a2,
+            IdealGasFunction::IdealGasHelmholtzLogTau { a } => tau.ln() * a,
+            IdealGasFunction::IdealGasHelmholtzPower { n, t } => tau.powf(t) * n,
+            IdealGasFunction::IdealGasHelmholtzPlanckEinstein { n, t } => {
+                (-(-tau * t).exp()).ln_1p() * n
+            }
+            IdealGasFunction::IdealGasHelmholtzPlanckEinsteinFunctionT { Tcrit, n, v } => {
+                (-(-tau * v / Tcrit).exp()).ln_1p() * n
+            }
+            IdealGasFunction::IdealGasHelmholtzPlanckEinsteinGeneralized { c, d, n, t } => {
+                ((tau * t).exp() * d + c).ln() * n
+            }
+            IdealGasFunction::IdealGasHelmholtzCP0AlyLee { T0, Tc, c } => {
+                let [a, b, c, d, e] = c;
+                let mut res = D::zero();
+                if a > 0.0 {
+                    let tau0 = Tc / T0;
+                    res += (-tau / tau0 + 1.0 + (tau / tau0).ln()) * a;
+                }
+                if b > 0.0 {
+                    res += (-(-tau * 2.0 * c / Tc).exp()).ln_1p() * b;
+                }
+                if d > 0.0 {
+                    res -= ((-tau * 2.0 * e / Tc).exp()).ln_1p() * d;
+                }
+                res
+            }
+            IdealGasFunction::IdealGasHelmholtzCP0Constant { T0, Tc, cp_over_R } => {
+                let tau0 = Tc / T0;
+                (-tau / tau0 + 1.0 + (tau / tau0).ln()) * cp_over_R
+            }
+            IdealGasFunction::IdealGasHelmholtzCP0PolyT { T0, Tc, c, t } => {
+                // unfortunately some models use floats and other models use 0 or -1 which needs to be treated separately...
+                if t.abs() < 10.0 * f64::EPSILON {
+                    let tau0 = Tc / T0;
+                    (-tau / tau0 + 1.0 + (tau / tau0).ln()) * c
+                } else if (t + 1.0).abs() < 10.0 * f64::EPSILON {
+                    let tau0 = Tc / T0;
+                    (-tau / Tc * (tau / tau0).ln() + (tau - tau0) / Tc) * c
+                } else {
+                    (-tau.powf(-t) * Tc.powf(t) / (t * (t + 1.0))
+                        - tau * T0.powf(t + 1.0) / (Tc * (t + 1.0))
+                        + T0.powf(t) / t)
+                        * c
+                }
+            }
+            IdealGasFunction::IdealGasHelmholtzEnthalpyEntropyOffset { a1, a2 } => tau * a2 + a1,
+        }
+    }
+}
-Original file line number
+Diff line change
@@ Expand Up / @@ -188,7 +188,7 @@ where @@
         }
     }
-    impl<E: Residual, N: Dim, D: DualNum<f64> + Copy> fmt::Display for State<E, N, D>
+    impl<E: Residual<N, D>, N: Dim, D: DualNum<f64> + Copy> fmt::Display for State<E, N, D>
     where
         DefaultAllocator: Allocator<N>,
     {
@@ Expand Down @@