diff --git a/src/network/include/gridfire/engine/engine_graph.h b/src/network/include/gridfire/engine/engine_graph.h
index b4a880d4..8eef8cc1 100644
--- a/src/network/include/gridfire/engine/engine_graph.h
+++ b/src/network/include/gridfire/engine/engine_graph.h
@@ -10,6 +10,8 @@
 #include "gridfire/engine/engine_abstract.h"
 #include "gridfire/screening/screening_abstract.h"
 #include "gridfire/screening/screening_types.h"
+#include "gridfire/partition/partition_abstract.h"
+#include "gridfire/partition/partition_ground.h"
 
 #include <string>
 #include <unordered_map>
@@ -101,6 +103,10 @@ namespace gridfire {
          */
         explicit GraphEngine(const fourdst::composition::Composition &composition);
 
+        explicit GraphEngine(const fourdst::composition::Composition &composition,
+                             const partition::PartitionFunction& partitionFunction
+                             );
+
         /**
          * @brief Constructs a GraphEngine from a set of reactions.
          *
@@ -307,6 +313,14 @@ namespace gridfire {
 
         [[nodiscard]] bool isPrecomputationEnabled() const;
 
+        [[nodiscard]] const partition::PartitionFunction& getPartitionFunction() const;
+
+        [[nodiscard]] double calculateReverseRate(
+            const reaction::Reaction &reaction,
+            double T9,
+            double expFactor
+        ) const;
+
     private:
         struct PrecomputedReaction {
             size_t reaction_index;
@@ -321,6 +335,7 @@ namespace gridfire {
             const double u = Constants::getInstance().get("u").value; ///< Atomic mass unit in g.
             const double Na = Constants::getInstance().get("N_a").value; ///< Avogadro's number.
             const double c = Constants::getInstance().get("c").value; ///< Speed of light in cm/s.
+            const double kB = Constants::getInstance().get("kB").value; ///< Boltzmann constant in erg/K.
         };
 
     private:
@@ -347,6 +362,7 @@ namespace gridfire {
         bool m_usePrecomputation = true; ///< Flag to enable or disable using precomputed reactions for efficiency. Mathematically, this should not change the results. Generally end users should not need to change this.
 
         std::vector<PrecomputedReaction> m_precomputedReactions; ///< Precomputed reactions for efficiency.
+        std::unique_ptr<partition::PartitionFunction> m_partitionFunction; ///< Partition function for the network.
 
     private:
         /**
@@ -432,6 +448,20 @@ namespace gridfire {
             double T9
         );
 
+
+        double calculateReverseRateTwoBody(
+            const reaction::Reaction &reaction,
+            const double T9,
+            const double forwardRate,
+            const double expFactor
+        ) const;
+
+        double GraphEngine::calculateReverseRateTwoBodyDerivative(
+            const reaction::Reaction &reaction,
+            const double T9,
+            const double reverseRate
+        ) const;
+
         [[nodiscard]] StepDerivatives<double> calculateAllDerivativesUsingPrecomputation(
             const std::vector<double> &Y_in,
             const std::vector<double>& bare_rates,
@@ -647,4 +677,36 @@ namespace gridfire {
         //       the entire network.
         return molar_concentration_product * k_reaction * threshold_flag;
     }
+
+    class AtomicReverseRate final : public CppAD::atomic_base<double> {
+    public:
+        AtomicReverseRate(
+            const reaction::Reaction& reaction,
+            const GraphEngine& engine
+        ):
+        atomic_base<double>("AtomicReverseRate"),
+        m_reaction(reaction),
+        m_engine(engine) {}
+
+        bool forward(
+            size_t p,
+            size_t q,
+            const CppAD::vector<bool>& vx,
+            CppAD::vector<bool>& vy,
+            const CppAD::vector<double>& tx,
+            CppAD::vector<double>& ty
+        ) override;
+        bool reverse(
+            size_t id,
+            size_t an,
+            const CppAD::vector<double>& tx,
+            const CppAD::vector<double>& ty,
+            CppAD::vector<double>& px,
+            const CppAD::vector<double>& py
+        );
+    private:
+        const double m_kB = Constants::getInstance().get("k_b").value; ///< Boltzmann constant in erg/K.
+        const reaction::Reaction& m_reaction;
+        const GraphEngine& m_engine;
+    };
 };
\ No newline at end of file
diff --git a/src/network/include/gridfire/partition/composite/partition_composite.h b/src/network/include/gridfire/partition/composite/partition_composite.h
index 11a11832..1d6e0ea8 100644
--- a/src/network/include/gridfire/partition/composite/partition_composite.h
+++ b/src/network/include/gridfire/partition/composite/partition_composite.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "gridfire/partition/partition_abstract.h"
+#include "gridfire/partition/partition_types.h"
 
 #include "fourdst/logging/logging.h"
 
@@ -12,28 +13,17 @@
 
 
 namespace gridfire::partition {
-    enum BasePartitionType {
-        RauscherThielemann, ///< Rauscher-Thielemann partition function
-        GroundState,        ///< Ground state partition function
-    };
-
-    inline std::unordered_map<BasePartitionType, std::string> basePartitionTypeToString = {
-        {RauscherThielemann, "RauscherThielemann"},
-        {GroundState, "GroundState"}
-    };
-
-    inline std::unordered_map<std::string, BasePartitionType> stringToBasePartitionType = {
-        {"RauscherThielemann", RauscherThielemann},
-        {"GroundState", GroundState}
-    };
-
     class CompositePartitionFunction final : public PartitionFunction {
     public:
         explicit CompositePartitionFunction(const std::vector<BasePartitionType>& partitionFunctions);
-        double evaluate(int z, int a, double T9) const override;
-        double evaluateDerivative(int z, int a, double T9) const override;
-        bool supports(int z, int a) const override;
-        std::string type() const override;
+        CompositePartitionFunction(const CompositePartitionFunction& other);
+        [[nodiscard]] double evaluate(int z, int a, double T9) const override;
+        [[nodiscard]] double evaluateDerivative(int z, int a, double T9) const override;
+        [[nodiscard]] bool supports(int z, int a) const override;
+        [[nodiscard]] std::string type() const override;
+        [[nodiscard]] std::unique_ptr<PartitionFunction> clone() const override {
+            return std::make_unique<CompositePartitionFunction>(*this);
+        }
     private:
         quill::Logger* m_logger = fourdst::logging::LogManager::getInstance().getLogger("log");
         std::vector<std::unique_ptr<PartitionFunction>> m_partitionFunctions; ///< Set of partition functions to use in the composite partition function.
diff --git a/src/network/include/gridfire/partition/partition_abstract.h b/src/network/include/gridfire/partition/partition_abstract.h
index 264f0e9c..c67e5774 100644
--- a/src/network/include/gridfire/partition/partition_abstract.h
+++ b/src/network/include/gridfire/partition/partition_abstract.h
@@ -1,14 +1,16 @@
 #pragma once
 
 #include <string>
+#include <memory>
 
 namespace gridfire::partition {
     class PartitionFunction {
     public:
         virtual ~PartitionFunction() = default;
-        virtual double evaluate(int z, int a, double T9) const = 0;
-        virtual double evaluateDerivative(int z, int a, double T9) const = 0;
-        virtual bool supports(int z, int a) const = 0;
-        virtual std::string type() const = 0;
+        [[nodiscard]] virtual double evaluate(int z, int a, double T9) const = 0;
+        [[nodiscard]] virtual double evaluateDerivative(int z, int a, double T9) const = 0;
+        [[nodiscard]] virtual bool supports(int z, int a) const = 0;
+        [[nodiscard]] virtual std::string type() const = 0;
+        [[nodiscard]] virtual std::unique_ptr<PartitionFunction> clone() const = 0;
     };
 }
\ No newline at end of file
diff --git a/src/network/include/gridfire/partition/partition_ground.h b/src/network/include/gridfire/partition/partition_ground.h
index 63cc3c45..a372f1ca 100644
--- a/src/network/include/gridfire/partition/partition_ground.h
+++ b/src/network/include/gridfire/partition/partition_ground.h
@@ -5,6 +5,7 @@
 #include "fourdst/logging/logging.h"
 
 #include <unordered_map>
+#include <memory>
 
 #include "quill/Logger.h"
 
@@ -27,6 +28,9 @@ namespace gridfire::partition {
             const int a
         ) const override;
         std::string type() const override { return "GroundState"; }
+        std::unique_ptr<PartitionFunction> clone() const override {
+            return std::make_unique<GroundStatePartitionFunction>(*this);
+        }
     private:
         quill::Logger* m_logger = fourdst::logging::LogManager::getInstance().getLogger("log");
         std::unordered_map<int, double> m_ground_state_spin;
diff --git a/src/network/include/gridfire/partition/partition_rauscher_thielemann.h b/src/network/include/gridfire/partition/partition_rauscher_thielemann.h
index 1cb4ac4d..3df61a16 100644
--- a/src/network/include/gridfire/partition/partition_rauscher_thielemann.h
+++ b/src/network/include/gridfire/partition/partition_rauscher_thielemann.h
@@ -9,6 +9,7 @@
 #include <unordered_map>
 #include <array>
 #include <utility>
+#include <memory>
 
 namespace gridfire::partition {
     class RauscherThielemannPartitionFunction final : public PartitionFunction {
@@ -41,6 +42,9 @@ namespace gridfire::partition {
             size_t upperIndex;
             size_t lowerIndex;
         };
+        std::unique_ptr<PartitionFunction> clone() const override {
+            return std::make_unique<RauscherThielemannPartitionFunction>(*this);
+        }
     private:
         quill::Logger* m_logger = fourdst::logging::LogManager::getInstance().getLogger("log");
         std::unordered_map<int, IsotopeData> m_partitionData;
diff --git a/src/network/include/gridfire/partition/partition_types.h b/src/network/include/gridfire/partition/partition_types.h
new file mode 100644
index 00000000..0d930f31
--- /dev/null
+++ b/src/network/include/gridfire/partition/partition_types.h
@@ -0,0 +1,21 @@
+#pragma once
+
+#include <unordered_map>
+#include <string>
+
+namespace gridfire::partition {
+    enum BasePartitionType {
+        RauscherThielemann, ///< Rauscher-Thielemann partition function
+        GroundState,        ///< Ground state partition function
+    };
+
+    inline std::unordered_map<BasePartitionType, std::string> basePartitionTypeToString = {
+        {RauscherThielemann, "RauscherThielemann"},
+        {GroundState, "GroundState"}
+    };
+
+    inline std::unordered_map<std::string, BasePartitionType> stringToBasePartitionType = {
+        {"RauscherThielemann", RauscherThielemann},
+        {"GroundState", GroundState}
+    };
+}
\ No newline at end of file
diff --git a/src/network/include/gridfire/partition/rauscher_thielemann_partition_data_record.h b/src/network/include/gridfire/partition/rauscher_thielemann_partition_data_record.h
index fc36399d..c9d7a099 100644
--- a/src/network/include/gridfire/partition/rauscher_thielemann_partition_data_record.h
+++ b/src/network/include/gridfire/partition/rauscher_thielemann_partition_data_record.h
@@ -8,7 +8,6 @@ namespace gridfire::partition::record {
         uint32_t z; ///< Atomic number
         uint32_t a; ///< Mass number
         double ground_state_spin; ///< Ground state spin
-        double partition_function; ///< Partition function value
         double normalized_g_values[24]; ///< Normalized g-values for the first 24 energy levels
     };
 #pragma pack(pop)
diff --git a/src/network/include/gridfire/reaction/reaction.h b/src/network/include/gridfire/reaction/reaction.h
index b51840e7..1adc193b 100644
--- a/src/network/include/gridfire/reaction/reaction.h
+++ b/src/network/include/gridfire/reaction/reaction.h
@@ -113,6 +113,8 @@ namespace gridfire::reaction {
          */
         [[nodiscard]] virtual CppAD::AD<double> calculate_rate(const CppAD::AD<double> T9) const;
 
+        [[nodiscard]] virtual double calculate_forward_rate_log_derivative(const double T9) const;
+
         /**
          * @brief Gets the reaction name in (projectile, ejectile) notation.
          * @return The reaction name (e.g., "p(p,g)d").
@@ -341,6 +343,8 @@ namespace gridfire::reaction {
          */
         [[nodiscard]] double calculate_rate(const double T9) const override;
 
+        [[nodiscard]] virtual double calculate_forward_rate_log_derivative(const double T9) const override;
+
         /**
          * @brief Calculates the total reaction rate using CppAD types.
          * @param T9 The temperature in units of 10^9 K, as a CppAD::AD<double>.
diff --git a/src/network/lib/engine/engine_graph.cpp b/src/network/lib/engine/engine_graph.cpp
index 22d908eb..8845372c 100644
--- a/src/network/lib/engine/engine_graph.cpp
+++ b/src/network/lib/engine/engine_graph.cpp
@@ -18,6 +18,7 @@
 #include <utility>
 #include <vector>
 #include <fstream>
+#include <ranges>
 
 #include <boost/numeric/odeint.hpp>
 
@@ -26,7 +27,18 @@ namespace gridfire {
     GraphEngine::GraphEngine(
         const fourdst::composition::Composition &composition
     ):
-     m_reactions(build_reaclib_nuclear_network(composition, false)) {
+     m_reactions(build_reaclib_nuclear_network(composition, false)),
+     m_partitionFunction(std::make_unique<partition::GroundStatePartitionFunction>()){
+        syncInternalMaps();
+        precomputeNetwork();
+    }
+
+    GraphEngine::GraphEngine(
+        const fourdst::composition::Composition &composition,
+        const partition::PartitionFunction& partitionFunction) :
+    m_reactions(build_reaclib_nuclear_network(composition, false)),
+    m_partitionFunction(partitionFunction.clone())  // Clone the partition function to ensure ownership
+    {
         syncInternalMaps();
         precomputeNetwork();
     }
@@ -220,6 +232,129 @@ namespace gridfire {
         }
     }
 
+    double GraphEngine::calculateReverseRate(
+        const reaction::Reaction &reaction,
+        const double T9,
+        const double expFactor
+    ) const {
+        double reverseRate = 0.0;
+        const double forwardRate = reaction.calculate_rate(T9);
+
+        if (reaction.reactants().size() == 2 && reaction.products().size() == 2) {
+            reverseRate = calculateReverseRateTwoBody(reaction, T9, forwardRate, expFactor);
+        } else {
+            LOG_WARNING(m_logger, "Reverse rate calculation for reactions with more than two reactants or products is not implemented.");
+        }
+        return reverseRate;
+    }
+
+    double GraphEngine::calculateReverseRateTwoBody(
+        const reaction::Reaction &reaction,
+        const double T9,
+        const double forwardRate,
+        const double expFactor
+    ) const {
+        std::vector<double> reactantPartitionFunctions;
+        std::vector<double> productPartitionFunctions;
+
+        reactantPartitionFunctions.reserve(reaction.reactants().size());
+        productPartitionFunctions.reserve(reaction.products().size());
+
+        std::unordered_map<fourdst::atomic::Species, int> reactantMultiplicity;
+        std::unordered_map<fourdst::atomic::Species, int> productMultiplicity;
+
+        reactantMultiplicity.reserve(reaction.reactants().size());
+        productMultiplicity.reserve(reaction.products().size());
+
+        for (const auto& reactant : reaction.reactants()) {
+            reactantMultiplicity[reactant] += 1;
+        }
+        for (const auto& product : reaction.products()) {
+            productMultiplicity[product] += 1;
+        }
+        double reactantSymmetryFactor = 1.0;
+        double productSymmetryFactor = 1.0;
+        for (const auto& count : reactantMultiplicity | std::views::values) {
+            reactantSymmetryFactor *= std::tgamma(count + 1);
+        }
+        for (const auto& count : productMultiplicity | std::views::values) {
+            productSymmetryFactor *= std::tgamma(count + 1);
+        }
+        const double symmetryFactor = reactantSymmetryFactor / productSymmetryFactor;
+
+        // Accumulate mass terms
+        auto mass_op = [](double acc, const auto& species) { return acc * species.a(); };
+        const double massNumerator = std::accumulate(
+            reaction.reactants().begin(),
+            reaction.reactants().end(),
+            1.0,
+            mass_op
+        );
+        const double massDenominator = std::accumulate(
+            reaction.products().begin(),
+            reaction.products().end(),
+            1.0,
+            mass_op
+        );
+
+        // Accumulate partition functions
+        auto pf_op = [&](double acc, const auto& species) { return acc * m_partitionFunction->evaluate(species.z(), species.a(), T9); };
+        const double partitionFunctionNumerator = std::accumulate(
+            reaction.reactants().begin(),
+            reaction.reactants().end(),
+            1.0,
+            pf_op
+        );
+        const double partitionFunctionDenominator = std::accumulate(
+            reaction.products().begin(),
+            reaction.products().end(),
+            1.0,
+            pf_op
+        );
+
+        const double CT = std::pow(massNumerator/massDenominator, 1.5) * (partitionFunctionNumerator/partitionFunctionDenominator);
+
+        return forwardRate * symmetryFactor * CT * expFactor;
+
+    }
+
+    double GraphEngine::calculateReverseRateTwoBodyDerivative(
+        const reaction::Reaction &reaction,
+        const double T9,
+        const double reverseRate
+    ) const {
+        const double d_log_kFwd = reaction.calculate_forward_rate_log_derivative(T9);
+
+        auto log_deriv_pf_op = [&](double acc, const auto& species) {
+            const double g = m_partitionFunction->evaluate(species.z(), species.a(), T9);
+            const double dg_dT = m_partitionFunction->evaluateDerivative(species.z(), species.a(), T9);
+            return (g == 0.0) ? acc : acc + (dg_dT / g);
+        };
+
+        const double reactant_log_derivative_sum = std::accumulate(
+            reaction.reactants().begin(),
+            reaction.reactants().end(),
+            0.0,
+            log_deriv_pf_op
+        );
+
+        const double product_log_derivative_sum = std::accumulate(
+            reaction.products().begin(),
+            reaction.products().end(),
+            0.0,
+            log_deriv_pf_op
+        );
+
+        const double d_log_C = reactant_log_derivative_sum - product_log_derivative_sum;
+
+        const double d_log_exp = reaction.qValue() / (m_constants.kB * T9 * T9);
+
+        const double log_total_derivative = d_log_kFwd + d_log_C + d_log_exp;
+
+        return reverseRate * log_total_derivative; // Return the derivative of the reverse rate with respect to T9
+
+    }
+
     StepDerivatives<double> GraphEngine::calculateAllDerivativesUsingPrecomputation(
         const std::vector<double> &Y_in,
         const std::vector<double> &bare_rates,
@@ -374,6 +509,10 @@ namespace gridfire {
         return m_usePrecomputation;
     }
 
+    const partition::PartitionFunction & GraphEngine::getPartitionFunction() const {
+        return *m_partitionFunction;
+    }
+
     double GraphEngine::calculateMolarReactionFlow(
         const reaction::Reaction &reaction,
         const std::vector<double> &Y,
@@ -648,4 +787,21 @@ namespace gridfire {
             m_precomputedReactions.push_back(std::move(precomp));
         }
     }
+
+    bool AtomicReverseRate::forward(
+        const size_t p,
+        const size_t q,
+        const CppAD::vector<bool> &vx,
+        CppAD::vector<bool> &vy,
+        const CppAD::vector<double> &tx,
+        CppAD::vector<double> &ty
+    ) {
+        const double T9 = tx[0];
+        const double expFactor = std::exp(-m_reaction.qValue() / (m_kB * T9 * 1e9)); // Convert MeV to erg
+        if (p == 0) {
+            // --- Zeroth order forward sweep ---
+            const auto k_rev = m_engine.calculateReverseRate(m_reaction, T9, expFactor);
+        }
+    }
+
 }
diff --git a/src/network/lib/partition/composite/partition_composite.cpp b/src/network/lib/partition/composite/partition_composite.cpp
index 10e09692..7f00c7bd 100644
--- a/src/network/lib/partition/composite/partition_composite.cpp
+++ b/src/network/lib/partition/composite/partition_composite.cpp
@@ -17,6 +17,13 @@ namespace gridfire::partition {
         }
     }
 
+    CompositePartitionFunction::CompositePartitionFunction(const CompositePartitionFunction &other) {
+        m_partitionFunctions.reserve(other.m_partitionFunctions.size());
+        for (const auto& pf : other.m_partitionFunctions) {
+            m_partitionFunctions.push_back(pf->clone());
+        }
+    }
+
     double CompositePartitionFunction::evaluate(int z, int a, double T9) const {
         LOG_TRACE_L1(m_logger, "Evaluating partition function for Z={} A={} T9={}", z, a, T9);
         for (const auto& partitionFunction : m_partitionFunctions) {
diff --git a/src/network/lib/partition/partition_rauscher_thielemann.cpp b/src/network/lib/partition/partition_rauscher_thielemann.cpp
index 2f81755e..6a825241 100644
--- a/src/network/lib/partition/partition_rauscher_thielemann.cpp
+++ b/src/network/lib/partition/partition_rauscher_thielemann.cpp
@@ -9,6 +9,7 @@
 #include <algorithm>
 #include <vector>
 #include <array>
+#include <iostream>
 
 namespace gridfire::partition {
     static constexpr std::array<double, 24> RT_TEMPERATURE_GRID_T9 = {
@@ -25,8 +26,17 @@ namespace gridfire::partition {
             IsotopeData data;
             data.ground_state_spin = record.ground_state_spin;
             std::ranges::copy(record.normalized_g_values, data.normalized_g_values.begin());
+            const int key = make_key(record.z, record.a);
+            LOG_TRACE_L3_LIMIT_EVERY_N(
+                100,
+                m_logger,
+                "(EVERY 100) Adding Rauscher-Thielemann partition data for Z={} A={} (key={})",
+                record.z,
+                record.a,
+                key
+            );
 
-            m_partitionData[make_key(record.z, record.a)] = std::move(data);
+            m_partitionData[key] = std::move(data);
         }
     }
 
diff --git a/src/network/lib/reaction/reaction.cpp b/src/network/lib/reaction/reaction.cpp
index 9cb03ac8..1387eff6 100644
--- a/src/network/lib/reaction/reaction.cpp
+++ b/src/network/lib/reaction/reaction.cpp
@@ -44,6 +44,27 @@ namespace gridfire::reaction {
         return calculate_rate<CppAD::AD<double>>(T9);
     }
 
+    double Reaction::calculate_forward_rate_log_derivative(const double T9) const {
+        constexpr double r_p13 = 1.0 / 3.0;
+        constexpr double r_p53 = 5.0 / 3.0;
+        constexpr double r_p23 = 2.0 / 3.0;
+        constexpr double r_p43 = 4.0 / 3.0;
+
+        const double T9_m1 = 1.0 / T9;
+        const double T9_m23 = std::pow(T9, -r_p23);
+        const double T9_m43 = std::pow(T9, -r_p43);
+
+        const double d_log_k_fwd_dT9 =
+            -m_rateCoefficients.a1 * T9_m1 * T9_m1
+            - r_p13 * m_rateCoefficients.a2 * T9_m43
+            + r_p13 * m_rateCoefficients.a3 * T9_m23
+            + m_rateCoefficients.a4
+            + r_p53 * m_rateCoefficients.a5 * std::pow(T9, r_p23)
+            + m_rateCoefficients.a6 * T9_m1;
+
+        return d_log_k_fwd_dT9; // Return the derivative of the log rate with respect to T9
+    }
+
     bool Reaction::contains(const Species &species) const {
         return contains_reactant(species) || contains_product(species);
     }
@@ -194,6 +215,57 @@ namespace gridfire::reaction {
         return calculate_rate<double>(T9);
     }
 
+    double LogicalReaction::calculate_forward_rate_log_derivative(const double T9) const {
+        constexpr double r_p13 = 1.0 / 3.0;
+        constexpr double r_p53 = 5.0 / 3.0;
+        constexpr double r_p23 = 2.0 / 3.0;
+        constexpr double r_p43 = 4.0 / 3.0;
+
+        double totalRate = 0.0;
+        double totalRateDerivative = 0.0;
+
+
+        const double T9_m1 = 1.0 / T9;
+        const double T913 = std::pow(T9, r_p13);
+        const double T953 = std::pow(T9, r_p53);
+        const double logT9 = std::log(T9);
+
+        const double T9_m1_sq = T9_m1 * T9_m1;
+        const double T9_m23 = std::pow(T9, -r_p23);
+        const double T9_m43 = std::pow(T9, -r_p43);
+        const double T9_p23 = std::pow(T9, r_p23);
+
+
+        for (const auto& coeffs : m_rates) {
+            const double exponent = coeffs.a0 +
+                                    coeffs.a1 * T9_m1 +
+                                    coeffs.a2 / T913 +
+                                    coeffs.a3 * T913 +
+                                    coeffs.a4 * T9 +
+                                    coeffs.a5 * T953 +
+                                    coeffs.a6 * logT9;
+            const double individualRate = std::exp(exponent);
+
+            const double d_exponent_T9 =
+                -coeffs.a1 * T9_m1_sq
+                - r_p13 * coeffs.a2 * T9_m43
+                + r_p13 * coeffs.a3 * T9_m23
+                + coeffs.a4
+                + r_p53 * coeffs.a5 * T9_p23
+                + coeffs.a6 * T9_m1;
+
+            const double individualRateDerivative = individualRate * d_exponent_T9;
+            totalRate += individualRate;
+            totalRateDerivative += individualRateDerivative;
+        }
+
+        if (totalRate == 0.0) {
+            return 0.0; // Avoid division by zero
+        }
+
+        return totalRateDerivative / totalRate;
+    }
+
     CppAD::AD<double> LogicalReaction::calculate_rate(const CppAD::AD<double> T9) const {
         return calculate_rate<CppAD::AD<double>>(T9);
     }
diff --git a/tests/graphnet_sandbox/main.cpp b/tests/graphnet_sandbox/main.cpp
index 43106c6d..7116dfbe 100644
--- a/tests/graphnet_sandbox/main.cpp
+++ b/tests/graphnet_sandbox/main.cpp
@@ -4,6 +4,7 @@
 #include "gridfire/engine/engine_graph.h"
 #include "gridfire/engine/engine_approx8.h"
 #include "gridfire/engine/views/engine_adaptive.h"
+#include "gridfire/partition/partition_types.h"
 #include "gridfire/engine/views/engine_defined.h"
 #include "gridfire/io/network_file.h"
 
@@ -57,7 +58,7 @@ void quill_terminate_handler()
 int main() {
     g_previousHandler = std::set_terminate(quill_terminate_handler);
     quill::Logger* logger = fourdst::logging::LogManager::getInstance().getLogger("log");
-    logger->set_log_level(quill::LogLevel::TraceL3);
+    logger->set_log_level(quill::LogLevel::TraceL2);
     LOG_DEBUG(logger, "Starting Adaptive Engine View Example...");
 
     using namespace gridfire;
@@ -93,13 +94,14 @@ int main() {
         BasePartitionType::RauscherThielemann,
         BasePartitionType::GroundState
     });
-    std::cout << "Partition Function for Mg-24: " << partitionFunction.evaluate(12, 24, 1.5) << std::endl;
-    std::cout << "Partition Function for F-23: " << partitionFunction.evaluate(9, 23, 1.5) << std::endl;
-    std::cout << "Partition Function for O-13: " << partitionFunction.evaluate(8, 13, 1.5) << std::endl;
+    std::cout << "Partition Function for Mg-24: " << partitionFunction.evaluate(12, 24, 8) << std::endl;
+    std::cout << "Partition Function for F-23: " << partitionFunction.evaluate(9, 23, 8) << std::endl;
+    std::cout << "Partition Function for O-13: " << partitionFunction.evaluate(8, 13, 8) << std::endl;
 
     netIn.dt0 = 1e-15;
 
-    // GraphEngine ReaclibEngine(composition);
+    GraphEngine ReaclibEngine(composition, partitionFunction);
+    std::cout << ReaclibEngine.getPartitionFunction().type() << std::endl;
     // ReaclibEngine.setPrecomputation(true);
     // // AdaptiveEngineView adaptiveEngine(ReaclibEngine);
     // io::SimpleReactionListFileParser parser{};
diff --git a/utils/RauscherThielemann2000/format.py b/utils/RauscherThielemann2000/format.py
index 6bc017ca..1bdb7ca5 100644
--- a/utils/RauscherThielemann2000/format.py
+++ b/utils/RauscherThielemann2000/format.py
@@ -31,6 +31,7 @@ def generate_binary_file(input_filepath, output_filepath):
             spin = float(match.group('spin'))
             coeffs_str = match.group('coeffs')
             g_values = [float(val) for val in coeffs_str.split()]
+            print(f"Processing Z={z}, A={a}, Spin={spin}")
 
             if len(g_values) != 24:
                 print(f"Warning: Found {len(g_values)} coefficients for Z={z}, A={a}. Expected 24. Skipping.")