Fix Redlich-Kwong equilibrium calculations

include/cantera/thermo/IdealSolidSolnPhase.h

@@ -596,7 +596,7 @@ class IdealSolidSolnPhase : public ThermoPhase
     virtual bool addSpecies(shared_ptr<Species> spec);
     virtual void initThermo();
     virtual void initThermoXML(XML_Node& phaseNode, const std::string& id);
-    virtual void setToEquilState(const doublereal* lambda_RT);
+    virtual void setToEquilState(const doublereal* mu_RT);
 
     //! Set the form for the standard and generalized concentrations
     /*!

include/cantera/thermo/RedlichKwongMFTP.h

@@ -176,7 +176,6 @@ class RedlichKwongMFTP : public MixtureFugacityTP
 
     virtual bool addSpecies(shared_ptr<Species> spec);
     virtual void setParametersFromXML(const XML_Node& thermoNode);
-    virtual void setToEquilState(const doublereal* lambda_RT);
     virtual void initThermoXML(XML_Node& phaseNode, const std::string& id);
     virtual void initThermo();
 

include/cantera/thermo/ThermoPhase.h

@@ -1457,10 +1457,10 @@ class ThermoPhase : public Phase
      * temperature is unchanged.  Any phase (ideal or not) that
      * implements this method can be equilibrated by ChemEquil.
      *
-     * @param lambda_RT Input vector of dimensionless element potentials
-     *                  The length is equal to nElements().
+     * @param mu_RT Input vector of dimensionless chemical potentials
+     *                  The length is equal to nSpecies().
      */
-    virtual void setToEquilState(const doublereal* lambda_RT) {
+    virtual void setToEquilState(const doublereal* mu_RT) {
         throw NotImplementedError("ThermoPhase::setToEquilState");
     }
 

interfaces/cython/cantera/test/test_equilibrium.py

@@ -216,3 +216,13 @@ def test_vcs(self):
 
     def test_vcs_est(self):
         self.solve('vcs', estimate_equil=-1)
+
+
+class Test_IdealSolidSolnPhase_Equil(utilities.CanteraTest):
+    def test_equil(self):
+        gas = ct.ThermoPhase('IdealSolidSolnPhaseExample.xml')
+        gas.TPX = 500, ct.one_atm, 'C2H2-graph: 1.0'
+
+        gas.equilibrate('TP', solver='element_potential')
+        self.assertNear(gas['C-graph'].X[0], 2.0 / 3.0)
+        self.assertNear(gas['H2-solute'].X[0], 1.0 / 3.0)

src/thermo/IdealSolidSolnPhase.cpp

@@ -447,21 +447,28 @@ void IdealSolidSolnPhase::initThermoXML(XML_Node& phaseNode, const std::string&
     ThermoPhase::initThermoXML(phaseNode, id_);
 }
 
-void IdealSolidSolnPhase::setToEquilState(const doublereal* lambda_RT)
+void IdealSolidSolnPhase::setToEquilState(const doublereal* mu_RT)
 {
     const vector_fp& grt = gibbs_RT_ref();
 
-    // set the pressure and composition to be consistent with the temperature
     doublereal pres = 0.0;
+    double m_p0 = refPressure();
     for (size_t k = 0; k < m_kk; k++) {
-        m_pp[k] = -grt[k];
-        for (size_t m = 0; m < nElements(); m++) {
-            m_pp[k] += nAtoms(k,m)*lambda_RT[m];
+        double tmp = -grt[k] + mu_RT[k];
+        if (tmp < -600.) {
+            m_pp[k] = 0.0;
+        } else if (tmp > 500.0) {
+            // Protect against inf results if the exponent is too high
+            double tmp2 = tmp / 500.;
+            tmp2 *= tmp2;
+            m_pp[k] = m_p0 * exp(500.) * tmp2;
+        } else {
+            m_pp[k] = m_p0 * exp(tmp);
         }
-        m_pp[k] = m_Pref * exp(m_pp[k]);
         pres += m_pp[k];
     }
-    setState_PX(pres, &m_pp[0]);
+    // set state
+    setState_PX(pres, m_pp.data());
 }
 
 void IdealSolidSolnPhase::setStandardConcentrationModel(const std::string& model)

src/thermo/RedlichKwongMFTP.cpp

@@ -518,36 +518,6 @@ doublereal RedlichKwongMFTP::critDensity() const
     return mmw / vc;
 }
 
-void RedlichKwongMFTP::setToEquilState(const doublereal* mu_RT)
-{
-    double tmp, tmp2;
-    _updateReferenceStateThermo();
-    getGibbs_RT_ref(m_tmpV.data());
-
-    // Within the method, we protect against inf results if the exponent is too
-    // high.
-    //
-    // If it is too low, we set the partial pressure to zero. This capability is
-    // needed by the elemental potential method.
-    doublereal pres = 0.0;
-    double m_p0 = refPressure();
-    for (size_t k = 0; k < m_kk; k++) {
-        tmp = -m_tmpV[k] + mu_RT[k];
-        if (tmp < -600.) {
-            m_pp[k] = 0.0;
-        } else if (tmp > 500.0) {
-            tmp2 = tmp / 500.;
-            tmp2 *= tmp2;
-            m_pp[k] = m_p0 * exp(500.) * tmp2;
-        } else {
-            m_pp[k] = m_p0 * exp(tmp);
-        }
-        pres += m_pp[k];
-    }
-    // set state
-    setState_PX(pres, &m_pp[0]);
-}
-
 bool RedlichKwongMFTP::addSpecies(shared_ptr<Species> spec)
 {
     bool added = MixtureFugacityTP::addSpecies(spec);