MargulesVPSSTP.cpp

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/**
 *  @file MargulesVPSSTP.cpp
 *   Definitions for ThermoPhase object for phases which
 *   employ excess Gibbs free energy formulations related to Margules
 *   expansions (see \ref thermoprops
 *    and class \link Cantera::MargulesVPSSTP MargulesVPSSTP\endlink).
 */

// This file is part of Cantera. See License.txt in the top-level directory or
// at http://www.cantera.org/license.txt for license and copyright information.

#include "cantera/thermo/MargulesVPSSTP.h"
#include "cantera/thermo/ThermoFactory.h"
#include "cantera/base/stringUtils.h"
#include "cantera/base/ctml.h"

using namespace std;

namespace Cantera
{
MargulesVPSSTP::MargulesVPSSTP() :
    numBinaryInteractions_(0),
    formMargules_(0),
    formTempModel_(0)
{
}

MargulesVPSSTP::MargulesVPSSTP(const std::string& inputFile, const std::string& id_) :
    numBinaryInteractions_(0),
    formMargules_(0),
    formTempModel_(0)
{
    initThermoFile(inputFile, id_);
}

MargulesVPSSTP::MargulesVPSSTP(XML_Node& phaseRoot, const std::string& id_) :
    numBinaryInteractions_(0),
    formMargules_(0),
    formTempModel_(0)
{
    importPhase(phaseRoot, this);
}

MargulesVPSSTP::MargulesVPSSTP(const MargulesVPSSTP& b)
{
    MargulesVPSSTP::operator=(b);
}

MargulesVPSSTP& MargulesVPSSTP::operator=(const MargulesVPSSTP& b)
{
    if (&b == this) {
        return *this;
    }

    GibbsExcessVPSSTP::operator=(b);

    numBinaryInteractions_ = b.numBinaryInteractions_;
    m_HE_b_ij = b.m_HE_b_ij;
    m_HE_c_ij = b.m_HE_c_ij;
    m_HE_d_ij = b.m_HE_d_ij;
    m_SE_b_ij = b.m_SE_b_ij;
    m_SE_c_ij = b.m_SE_c_ij;
    m_SE_d_ij = b.m_SE_d_ij;
    m_VHE_b_ij = b.m_VHE_b_ij;
    m_VHE_c_ij = b.m_VHE_c_ij;
    m_VHE_d_ij = b.m_VHE_d_ij;
    m_VSE_b_ij = b.m_VSE_b_ij;
    m_VSE_c_ij = b.m_VSE_c_ij;
    m_VSE_d_ij = b.m_VSE_d_ij;
    m_pSpecies_A_ij = b.m_pSpecies_A_ij;
    m_pSpecies_B_ij = b.m_pSpecies_B_ij;
    formMargules_ = b.formMargules_;
    formTempModel_ = b.formTempModel_;

    return *this;
}

ThermoPhase* MargulesVPSSTP::duplMyselfAsThermoPhase() const
{
    return new MargulesVPSSTP(*this);
}

// -- Activities, Standard States, Activity Concentrations -----------

void MargulesVPSSTP::getLnActivityCoefficients(doublereal* lnac) const
{
    // Update the activity coefficients
    s_update_lnActCoeff();

    // take the exp of the internally stored coefficients.
    for (size_t k = 0; k < m_kk; k++) {
        lnac[k] = lnActCoeff_Scaled_[k];
    }
}

// ------------ Partial Molar Properties of the Solution ------------

void MargulesVPSSTP::getChemPotentials(doublereal* mu) const
{
    // First get the standard chemical potentials in molar form. This requires
    // updates of standard state as a function of T and P
    getStandardChemPotentials(mu);

    // Update the activity coefficients
    s_update_lnActCoeff();
    for (size_t k = 0; k < m_kk; k++) {
        double xx = std::max(moleFractions_[k], SmallNumber);
        mu[k] += RT() * (log(xx) + lnActCoeff_Scaled_[k]);
    }
}

doublereal MargulesVPSSTP::enthalpy_mole() const
{
    size_t kk = nSpecies();
    double h = 0;
    vector_fp hbar(kk);
    getPartialMolarEnthalpies(&hbar[0]);
    for (size_t i = 0; i < kk; i++) {
        h += moleFractions_[i]*hbar[i];
    }
    return h;
}

doublereal MargulesVPSSTP::entropy_mole() const
{
    size_t kk = nSpecies();
    double s = 0;
    vector_fp sbar(kk);
    getPartialMolarEntropies(&sbar[0]);
    for (size_t i = 0; i < kk; i++) {
        s += moleFractions_[i]*sbar[i];
    }
    return s;
}

doublereal MargulesVPSSTP::cp_mole() const
{
    size_t kk = nSpecies();
    double cp = 0;
    vector_fp cpbar(kk);
    getPartialMolarCp(&cpbar[0]);
    for (size_t i = 0; i < kk; i++) {
        cp += moleFractions_[i]*cpbar[i];
    }
    return cp;
}

doublereal MargulesVPSSTP::cv_mole() const
{
    return cp_mole() - GasConstant;
}

void MargulesVPSSTP::getPartialMolarEnthalpies(doublereal* hbar) const
{
    // Get the nondimensional standard state enthalpies
    getEnthalpy_RT(hbar);

    // dimensionalize it.
    for (size_t k = 0; k < m_kk; k++) {
        hbar[k] *= RT();
    }

    // Update the activity coefficients, This also update the internally stored
    // molalities.
    s_update_lnActCoeff();
    s_update_dlnActCoeff_dT();
    for (size_t k = 0; k < m_kk; k++) {
        hbar[k] -= RT() * temperature() * dlnActCoeffdT_Scaled_[k];
    }
}

void MargulesVPSSTP::getPartialMolarCp(doublereal* cpbar) const
{
    // Get the nondimensional standard state entropies
    getCp_R(cpbar);
    double T = temperature();

    // Update the activity coefficients, This also update the internally stored
    // molalities.
    s_update_lnActCoeff();
    s_update_dlnActCoeff_dT();

    for (size_t k = 0; k < m_kk; k++) {
        cpbar[k] -= 2 * T * dlnActCoeffdT_Scaled_[k] + T * T * d2lnActCoeffdT2_Scaled_[k];
    }
    // dimensionalize it.
    for (size_t k = 0; k < m_kk; k++) {
        cpbar[k] *= GasConstant;
    }
}

void MargulesVPSSTP::getPartialMolarEntropies(doublereal* sbar) const
{
    // Get the nondimensional standard state entropies
    getEntropy_R(sbar);
    double T = temperature();

    // Update the activity coefficients, This also update the internally stored
    // molalities.
    s_update_lnActCoeff();
    s_update_dlnActCoeff_dT();

    for (size_t k = 0; k < m_kk; k++) {
        double xx = std::max(moleFractions_[k], SmallNumber);
        sbar[k] += - lnActCoeff_Scaled_[k] -log(xx) - T * dlnActCoeffdT_Scaled_[k];
    }

    // dimensionalize it.
    for (size_t k = 0; k < m_kk; k++) {
        sbar[k] *= GasConstant;
    }
}

void MargulesVPSSTP::getPartialMolarVolumes(doublereal* vbar) const
{
    double T = temperature();

    // Get the standard state values in m^3 kmol-1
    getStandardVolumes(vbar);

    for (size_t i = 0; i < numBinaryInteractions_; i++) {
        size_t iA = m_pSpecies_A_ij[i];
        size_t iB = m_pSpecies_B_ij[i];
        double XA = moleFractions_[iA];
        double XB = moleFractions_[iB];
        double g0 = (m_VHE_b_ij[i] - T * m_VSE_b_ij[i]);
        double g1 = (m_VHE_c_ij[i] - T * m_VSE_c_ij[i]);
        const doublereal temp1 = g0 + g1 * XB;
        const doublereal all = -1.0*XA*XB*temp1 - XA*XB*XB*g1;

        for (size_t iK = 0; iK < m_kk; iK++) {
            vbar[iK] += all;
        }
        vbar[iA] += XB * temp1;
        vbar[iB] += XA * temp1 + XA*XB*g1;
    }
}

void MargulesVPSSTP::initThermo()
{
    initLengths();
    GibbsExcessVPSSTP::initThermo();
}

void MargulesVPSSTP::initLengths()
{
    dlnActCoeffdlnN_.resize(m_kk, m_kk);
}

void MargulesVPSSTP::initThermoXML(XML_Node& phaseNode, const std::string& id_)
{
    if ((int) id_.size() > 0) {
        string idp = phaseNode.id();
        if (idp != id_) {
            throw CanteraError("MargulesVPSSTP::initThermoXML", "phasenode and Id are incompatible");
        }
    }

    // Find the Thermo XML node
    if (!phaseNode.hasChild("thermo")) {
        throw CanteraError("MargulesVPSSTP::initThermoXML",
                           "no thermo XML node");
    }
    XML_Node& thermoNode = phaseNode.child("thermo");

    // Make sure that the thermo model is Margules
    if (!ba::iequals(thermoNode["model"], "margules")) {
        throw CanteraError("MargulesVPSSTP::initThermoXML",
                           "model name isn't Margules: " + thermoNode["model"]);
    }

    // Go get all of the coefficients and factors in the activityCoefficients
    // XML block
    if (thermoNode.hasChild("activityCoefficients")) {
        XML_Node& acNode = thermoNode.child("activityCoefficients");
        if (!ba::iequals(acNode["model"], "margules")) {
            throw CanteraError("MargulesVPSSTP::initThermoXML",
                               "Unknown activity coefficient model: " + acNode["model"]);
        }
        for (size_t i = 0; i < acNode.nChildren(); i++) {
            XML_Node& xmlACChild = acNode.child(i);

            // Process a binary salt field, or any of the other XML fields that
            // make up the Pitzer Database. Entries will be ignored if any of
            // the species in the entry isn't in the solution.
            if (ba::iequals(xmlACChild.name(), "binaryneutralspeciesparameters")) {
                readXMLBinarySpecies(xmlACChild);
            }
        }
    }

    // Go down the chain
    GibbsExcessVPSSTP::initThermoXML(phaseNode, id_);
}

void MargulesVPSSTP::s_update_lnActCoeff() const
{
    double T = temperature();
    lnActCoeff_Scaled_.assign(m_kk, 0.0);
    for (size_t i = 0; i < numBinaryInteractions_; i++) {
        size_t iA = m_pSpecies_A_ij[i];
        size_t iB = m_pSpecies_B_ij[i];
        double g0 = (m_HE_b_ij[i] - T * m_SE_b_ij[i]) / RT();
        double g1 = (m_HE_c_ij[i] - T * m_SE_c_ij[i]) / RT();
        double XA = moleFractions_[iA];
        double XB = moleFractions_[iB];
        const doublereal XAXB = XA * XB;
        const doublereal g0g1XB = (g0 + g1 * XB);
        const doublereal all = -1.0 * XAXB * g0g1XB - XAXB * XB * g1;
        for (size_t iK = 0; iK < m_kk; iK++) {
            lnActCoeff_Scaled_[iK] += all;
        }
        lnActCoeff_Scaled_[iA] += XB * g0g1XB;
        lnActCoeff_Scaled_[iB] += XA * g0g1XB + XAXB * g1;
    }
}

void MargulesVPSSTP::s_update_dlnActCoeff_dT() const
{
    doublereal invT = 1.0 / temperature();
    doublereal invRTT = 1.0 / GasConstant*invT*invT;
    dlnActCoeffdT_Scaled_.assign(m_kk, 0.0);
    d2lnActCoeffdT2_Scaled_.assign(m_kk, 0.0);
    for (size_t i = 0; i < numBinaryInteractions_; i++) {
        size_t iA = m_pSpecies_A_ij[i];
        size_t iB = m_pSpecies_B_ij[i];
        double XA = moleFractions_[iA];
        double XB = moleFractions_[iB];
        double g0 = -m_HE_b_ij[i] * invRTT;
        double g1 = -m_HE_c_ij[i] * invRTT;
        const doublereal XAXB = XA * XB;
        const doublereal g0g1XB = (g0 + g1 * XB);
        const doublereal all = -1.0 * XAXB * g0g1XB - XAXB * XB * g1;
        const doublereal mult = 2.0 * invT;
        const doublereal dT2all = mult * all;
        for (size_t iK = 0; iK < m_kk; iK++) {
            dlnActCoeffdT_Scaled_[iK] += all;
            d2lnActCoeffdT2_Scaled_[iK] -= dT2all;
        }
        dlnActCoeffdT_Scaled_[iA] += XB * g0g1XB;
        dlnActCoeffdT_Scaled_[iB] += XA * g0g1XB + XAXB * g1;
        d2lnActCoeffdT2_Scaled_[iA] -= mult * XB * g0g1XB;
        d2lnActCoeffdT2_Scaled_[iB] -= mult * (XA * g0g1XB + XAXB * g1);
    }
}

void MargulesVPSSTP::getdlnActCoeffdT(doublereal* dlnActCoeffdT) const
{
    s_update_dlnActCoeff_dT();
    for (size_t k = 0; k < m_kk; k++) {
        dlnActCoeffdT[k] = dlnActCoeffdT_Scaled_[k];
    }
}

void MargulesVPSSTP::getd2lnActCoeffdT2(doublereal* d2lnActCoeffdT2) const
{
    s_update_dlnActCoeff_dT();
    for (size_t k = 0; k < m_kk; k++) {
        d2lnActCoeffdT2[k] = d2lnActCoeffdT2_Scaled_[k];
    }
}

void MargulesVPSSTP::getdlnActCoeffds(const doublereal dTds, const doublereal* const dXds,
                                       doublereal* dlnActCoeffds) const
{
    double T = temperature();
    s_update_dlnActCoeff_dT();
    for (size_t iK = 0; iK < m_kk; iK++) {
        dlnActCoeffds[iK] = 0.0;
    }

    for (size_t i = 0; i < numBinaryInteractions_; i++) {
        size_t iA = m_pSpecies_A_ij[i];
        size_t iB = m_pSpecies_B_ij[i];
        double XA = moleFractions_[iA];
        double XB = moleFractions_[iB];
        double dXA = dXds[iA];
        double dXB = dXds[iB];
        double g0 = (m_HE_b_ij[i] - T * m_SE_b_ij[i]) / RT();
        double g1 = (m_HE_c_ij[i] - T * m_SE_c_ij[i]) / RT();
        const doublereal g02g1XB = g0 + 2*g1*XB;
        const doublereal g2XAdXB = 2*g1*XA*dXB;
        const doublereal all = (-XB * dXA - XA *dXB) * g02g1XB - XB *g2XAdXB;
        for (size_t iK = 0; iK < m_kk; iK++) {
            dlnActCoeffds[iK] += all + dlnActCoeffdT_Scaled_[iK]*dTds;
        }
        dlnActCoeffds[iA] += dXB * g02g1XB;
        dlnActCoeffds[iB] += dXA * g02g1XB + g2XAdXB;
    }
}

void MargulesVPSSTP::s_update_dlnActCoeff_dlnN_diag() const
{
    double T = temperature();
    dlnActCoeffdlnN_diag_.assign(m_kk, 0.0);

    for (size_t iK = 0; iK < m_kk; iK++) {
        double XK = moleFractions_[iK];

        for (size_t i = 0; i < numBinaryInteractions_; i++) {
            size_t iA = m_pSpecies_A_ij[i];
            size_t iB = m_pSpecies_B_ij[i];
            size_t delAK = 0;
            size_t delBK = 0;

            if (iA==iK) {
                delAK = 1;
            } else if (iB==iK) {
                delBK = 1;
            }

            double XA = moleFractions_[iA];
            double XB = moleFractions_[iB];

            double g0 = (m_HE_b_ij[i] - T * m_SE_b_ij[i]) / RT();
            double g1 = (m_HE_c_ij[i] - T * m_SE_c_ij[i]) / RT();

            dlnActCoeffdlnN_diag_[iK] += 2*(delBK-XB)*(g0*(delAK-XA)+g1*(2*(delAK-XA)*XB+XA*(delBK-XB)));
        }
        dlnActCoeffdlnN_diag_[iK] = XK*dlnActCoeffdlnN_diag_[iK];
    }
}

void MargulesVPSSTP::s_update_dlnActCoeff_dlnN() const
{
    double T = temperature();
    dlnActCoeffdlnN_.zero();

    // Loop over the activity coefficient gamma_k
    for (size_t iK = 0; iK < m_kk; iK++) {
        for (size_t iM = 0; iM < m_kk; iM++) {
            double XM = moleFractions_[iM];
            for (size_t i = 0; i < numBinaryInteractions_; i++) {
                size_t iA = m_pSpecies_A_ij[i];
                size_t iB = m_pSpecies_B_ij[i];
                double delAK = 0.0;
                double delBK = 0.0;
                double delAM = 0.0;
                double delBM = 0.0;
                if (iA==iK) {
                    delAK = 1.0;
                } else if (iB==iK) {
                    delBK = 1.0;
                }
                if (iA==iM) {
                    delAM = 1.0;
                } else if (iB==iM) {
                    delBM = 1.0;
                }

                double XA = moleFractions_[iA];
                double XB = moleFractions_[iB];
                double g0 = (m_HE_b_ij[i] - T * m_SE_b_ij[i]) / RT();
                double g1 = (m_HE_c_ij[i] - T * m_SE_c_ij[i]) / RT();
                dlnActCoeffdlnN_(iK,iM) += g0*((delAM-XA)*(delBK-XB)+(delAK-XA)*(delBM-XB));
                dlnActCoeffdlnN_(iK,iM) += 2*g1*((delAM-XA)*(delBK-XB)*XB+(delAK-XA)*(delBM-XB)*XB+(delBM-XB)*(delBK-XB)*XA);
            }
            dlnActCoeffdlnN_(iK,iM) = XM*dlnActCoeffdlnN_(iK,iM);
        }
    }
}

void MargulesVPSSTP::s_update_dlnActCoeff_dlnX_diag() const
{
    doublereal T = temperature();
    dlnActCoeffdlnX_diag_.assign(m_kk, 0.0);

    for (size_t i = 0; i < numBinaryInteractions_; i++) {
        size_t iA = m_pSpecies_A_ij[i];
        size_t iB = m_pSpecies_B_ij[i];

        doublereal XA = moleFractions_[iA];
        doublereal XB = moleFractions_[iB];

        doublereal g0 = (m_HE_b_ij[i] - T * m_SE_b_ij[i]) / RT();
        doublereal g1 = (m_HE_c_ij[i] - T * m_SE_c_ij[i]) / RT();

        dlnActCoeffdlnX_diag_[iA] += XA*XB*(2*g1*-2*g0-6*g1*XB);
        dlnActCoeffdlnX_diag_[iB] += XA*XB*(2*g1*-2*g0-6*g1*XB);
    }
}

void MargulesVPSSTP::getdlnActCoeffdlnN_diag(doublereal* dlnActCoeffdlnN_diag) const
{
    s_update_dlnActCoeff_dlnN_diag();
    for (size_t k = 0; k < m_kk; k++) {
        dlnActCoeffdlnN_diag[k] = dlnActCoeffdlnN_diag_[k];
    }
}

void MargulesVPSSTP::getdlnActCoeffdlnX_diag(doublereal* dlnActCoeffdlnX_diag) const
{
    s_update_dlnActCoeff_dlnX_diag();
    for (size_t k = 0; k < m_kk; k++) {
        dlnActCoeffdlnX_diag[k] = dlnActCoeffdlnX_diag_[k];
    }
}

void MargulesVPSSTP::getdlnActCoeffdlnN(const size_t ld, doublereal* dlnActCoeffdlnN)
{
    s_update_dlnActCoeff_dlnN();
    double* data =  & dlnActCoeffdlnN_(0,0);
    for (size_t k = 0; k < m_kk; k++) {
        for (size_t m = 0; m < m_kk; m++) {
            dlnActCoeffdlnN[ld * k + m] = data[m_kk * k + m];
        }
    }
}

void MargulesVPSSTP::resizeNumInteractions(const size_t num)
{
    numBinaryInteractions_ = num;
    m_HE_b_ij.resize(num, 0.0);
    m_HE_c_ij.resize(num, 0.0);
    m_HE_d_ij.resize(num, 0.0);
    m_SE_b_ij.resize(num, 0.0);
    m_SE_c_ij.resize(num, 0.0);
    m_SE_d_ij.resize(num, 0.0);
    m_VHE_b_ij.resize(num, 0.0);
    m_VHE_c_ij.resize(num, 0.0);
    m_VHE_d_ij.resize(num, 0.0);
    m_VSE_b_ij.resize(num, 0.0);
    m_VSE_c_ij.resize(num, 0.0);
    m_VSE_d_ij.resize(num, 0.0);

    m_pSpecies_A_ij.resize(num, npos);
    m_pSpecies_B_ij.resize(num, npos);
}

void MargulesVPSSTP::readXMLBinarySpecies(XML_Node& xmLBinarySpecies)
{
    string xname = xmLBinarySpecies.name();
    if (xname != "binaryNeutralSpeciesParameters") {
        throw CanteraError("MargulesVPSSTP::readXMLBinarySpecies",
                           "Incorrect name for processing this routine: " + xname);
    }
    vector_fp vParams;
    string aName = xmLBinarySpecies.attrib("speciesA");
    if (aName == "") {
        throw CanteraError("MargulesVPSSTP::readXMLBinarySpecies", "no speciesA attrib");
    }
    string bName = xmLBinarySpecies.attrib("speciesB");
    if (bName == "") {
        throw CanteraError("MargulesVPSSTP::readXMLBinarySpecies", "no speciesB attrib");
    }

    // Find the index of the species in the current phase. It's not an error to
    // not find the species. What this means is that the A-B interaction
    // referred to in this block will be ignored.
    size_t aSpecies = speciesIndex(aName);
    if (aSpecies == npos) {
        return;
    }
    string aspName = speciesName(aSpecies);

    // @TODO Figure out what the original reason is for putting an error
    //       condition for charged species. Seems OK to me.
    if (charge(aSpecies) != 0.0) {
        throw CanteraError("MargulesVPSSTP::readXMLBinarySpecies",
            "speciesA has a charge: {}", charge(aSpecies));
    }
    size_t bSpecies = speciesIndex(bName);
    if (bSpecies == npos) {
        return;
    }
    string bspName = speciesName(bSpecies);
    if (charge(bSpecies) != 0.0) {
        throw CanteraError("MargulesVPSSTP::readXMLBinarySpecies",
            "speciesB has a charge: {}", charge(bSpecies));
    }

    resizeNumInteractions(numBinaryInteractions_ + 1);
    size_t iSpot = numBinaryInteractions_ - 1;
    m_pSpecies_A_ij[iSpot] = aSpecies;
    m_pSpecies_B_ij[iSpot] = bSpecies;

    for (size_t iChild = 0; iChild < xmLBinarySpecies.nChildren(); iChild++) {
        XML_Node& xmlChild = xmLBinarySpecies.child(iChild);
        string nodeName = ba::to_lower_copy(xmlChild.name());

        // Process the binary species interaction parameters.
        // They are in subblocks labeled:
        //           excessEnthalpy
        //           excessEntropy
        //           excessVolume_Enthalpy
        //           excessVolume_Entropy
        // Other blocks are currently ignored.
        // @TODO determine a policy about ignoring blocks that should or shouldn't be there.
        if (nodeName == "excessenthalpy") {
            // Get the string containing all of the values
            getFloatArray(xmlChild, vParams, true, "toSI", "excessEnthalpy");
            if (vParams.size() != 2) {
                throw CanteraError("MargulesVPSSTP::readXMLBinarySpecies::excessEnthalpy for " + aspName
                                   + "::" + bspName,
                                   "wrong number of params found. Need 2");
            }
            m_HE_b_ij[iSpot] = vParams[0];
            m_HE_c_ij[iSpot] = vParams[1];
        }

        if (nodeName == "excessentropy") {
            // Get the string containing all of the values
            getFloatArray(xmlChild, vParams, true, "toSI", "excessEntropy");
            if (vParams.size() != 2) {
                throw CanteraError("MargulesVPSSTP::readXMLBinarySpecies::excessEntropy for " + aspName
                                   + "::" + bspName,
                                   "wrong number of params found. Need 2");
            }
            m_SE_b_ij[iSpot] = vParams[0];
            m_SE_c_ij[iSpot] = vParams[1];
        }

        if (nodeName == "excessvolume_enthalpy") {
            // Get the string containing all of the values
            getFloatArray(xmlChild, vParams, true, "toSI", "excessVolume_Enthalpy");
            if (vParams.size() != 2) {
                throw CanteraError("MargulesVPSSTP::readXMLBinarySpecies::excessVolume_Enthalpy for " + aspName
                                   + "::" + bspName,
                                   "wrong number of params found. Need 2");
            }
            m_VHE_b_ij[iSpot] = vParams[0];
            m_VHE_c_ij[iSpot] = vParams[1];
        }

        if (nodeName == "excessvolume_entropy") {
            // Get the string containing all of the values
            getFloatArray(xmlChild, vParams, true, "toSI", "excessVolume_Entropy");
            if (vParams.size() != 2) {
                throw CanteraError("MargulesVPSSTP::readXMLBinarySpecies::excessVolume_Entropy for " + aspName
                                   + "::" + bspName,
                                   "wrong number of params found. Need 2");
            }
            m_VSE_b_ij[iSpot] = vParams[0];
            m_VSE_c_ij[iSpot] = vParams[1];
        }
    }
}

}