diff --git a/MaterialLib/CMakeLists.txt b/MaterialLib/CMakeLists.txt
index afa6d7b9a21858d119b03df8e6dbbf80e3263f1f..9030788b9736d9f31f66128f0d669fa11b2217bd 100644
--- a/MaterialLib/CMakeLists.txt
+++ b/MaterialLib/CMakeLists.txt
@@ -7,6 +7,7 @@ append_source_files(SOURCES FractureModels)
append_source_files(SOURCES Fluid)
append_source_files(SOURCES Fluid/Density)
append_source_files(SOURCES Fluid/Viscosity)
+append_source_files(SOURCES Fluid/GibbsFreeEnergy)
append_source_files(SOURCES PorousMedium/Porosity)
append_source_files(SOURCES PorousMedium/Storage)
diff --git a/MaterialLib/Fluid/GibbsFreeEnergy/DimensionLessGibbsFreeEnergyRegion1.cpp b/MaterialLib/Fluid/GibbsFreeEnergy/DimensionLessGibbsFreeEnergyRegion1.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b1169ae488a45e0dd728bc91487b0467e80b319a
--- /dev/null
+++ b/MaterialLib/Fluid/GibbsFreeEnergy/DimensionLessGibbsFreeEnergyRegion1.cpp
@@ -0,0 +1,123 @@
+/**
+ * \brief Define members of the class for dimensionless Gibbs free energy.
+ *
+ * \copyright
+ * Copyright (c) 2012-2016, OpenGeoSys Community (http://www.opengeosys.org)
+ * Distributed under a Modified BSD License.
+ * See accompanying file LICENSE.txt or
+ * http://www.opengeosys.org/project/license
+ *
+ * \file DimensionLessGibbsFreeEnergyRegion1.cpp
+ *
+ * Created on December 8, 2016, 12:31 PM
+ */
+
+#include "DimensionLessGibbsFreeEnergyRegion1.h"
+
+#include <cmath>
+
+namespace MaterialLib
+{
+namespace Fluid
+{
+static const double ni[34] = {
+ 1.4632971213167E-01, -8.4548187169114E-01, -3.7563603672040E+00,
+ 3.3855169168385E+00, -9.5791963387872E-01, 1.5772038513228E-01,
+ -1.6616417199501E-02, 8.1214629983568E-04, 2.8319080123804E-04,
+ -6.0706301565874E-04, -1.8990068218419E-02, -3.2529748770505E-02,
+ -2.1841717175414E-02, -5.2838357969930E-05, -4.7184321073267E-04,
+ -3.0001780793026E-04, 4.7661393906987E-05, -4.4141845330846E-06,
+ -7.2694996297594E-16, -3.1679644845054E-05, -2.8270797985312E-06,
+ -8.5205128120103E-10, -2.2425281908000E-06, -6.5171222895601E-07,
+ -1.4341729937924E-13, -4.0516996860117E-07, -1.2734301741641E-09,
+ -1.7424871230634E-10, -6.8762131295531E-19, 1.4478307828521E-20,
+ 2.6335781662795E-23, -1.1947622640071E-23, 1.8228094581404E-24,
+ -9.35370872924580E-26};
+
+static const double li[34] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1,
+ 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4,
+ 4, 5, 8, 8, 21, 23, 29, 30, 31, 32};
+
+static const double ji[34] = {
+ -2, -1, 0, 1, 2, 3, 4, 5, -9, -7, -1, 0, 1, 3, -3, 0, 1,
+ 3, 17, -4, 0, 6, -5, -2, 10, -8, -11, -6, -29, -31, -38, -39, -40, -41};
+
+double DimensionLessGibbsFreeEnergyRegion1::get_gamma(const double tau,
+ const double pi) const
+{
+ double val = 0.;
+ for (int i = 0; i < 34; i++)
+ {
+ val += ni[i] * std::pow(7.1 - pi, li[i]) * std::pow(tau - 1.222, ji[i]);
+ }
+
+ return val;
+}
+
+double DimensionLessGibbsFreeEnergyRegion1::get_dgamma_dtau(
+ const double tau, const double pi) const
+{
+ double val = 0.;
+ for (int i = 0; i < 34; i++)
+ {
+ val += ni[i] * ji[i] * std::pow(7.1 - pi, li[i]) *
+ std::pow(tau - 1.222, ji[i] - 1.0);
+ }
+
+ return val;
+}
+
+double DimensionLessGibbsFreeEnergyRegion1::get_dgamma_dtau_dtau(
+ const double tau, const double pi) const
+{
+ double val = 0.;
+ for (int i = 0; i < 34; i++)
+ {
+ val += ni[i] * ji[i] * (ji[i] - 1.0) * std::pow(7.1 - pi, li[i]) *
+ std::pow(tau - 1.222, ji[i] - 2.0);
+ }
+
+ return val;
+}
+
+double DimensionLessGibbsFreeEnergyRegion1::get_dgamma_dpi(
+ const double tau, const double pi) const
+{
+ double val = 0.;
+ for (int i = 0; i < 34; i++)
+ {
+ val -= ni[i] * li[i] * std::pow(7.1 - pi, li[i] - 1.0) *
+ std::pow(tau - 1.222, ji[i]);
+ }
+
+ return val;
+}
+
+double DimensionLessGibbsFreeEnergyRegion1::get_dgamma_dpi_dpi(
+ const double tau, const double pi) const
+{
+ double val = 0.;
+ for (int i = 0; i < 34; i++)
+ {
+ val += ni[i] * li[i] * (li[i] - 1.0) * std::pow(7.1 - pi, li[i] - 2.0) *
+ std::pow(tau - 1.222, ji[i]);
+ }
+
+ return val;
+}
+
+double DimensionLessGibbsFreeEnergyRegion1::get_dgamma_dtau_dpi(
+ const double tau, const double pi) const
+{
+ double val = 0.;
+ for (int i = 0; i < 34; i++)
+ {
+ val -= ni[i] * ji[i] * li[i] * std::pow(7.1 - pi, li[i] - 1.0) *
+ std::pow(tau - 1.222, ji[i] - 1.0);
+ }
+
+ return val;
+}
+
+} // end namespace
+} // end namespace
diff --git a/MaterialLib/Fluid/GibbsFreeEnergy/DimensionLessGibbsFreeEnergyRegion1.h b/MaterialLib/Fluid/GibbsFreeEnergy/DimensionLessGibbsFreeEnergyRegion1.h
new file mode 100644
index 0000000000000000000000000000000000000000..0d4448199c621d165b26fbcd01380c14dcb8662f
--- /dev/null
+++ b/MaterialLib/Fluid/GibbsFreeEnergy/DimensionLessGibbsFreeEnergyRegion1.h
@@ -0,0 +1,100 @@
+/**
+ * \brief Declare a class for dimensionless Gibbs free energy, region1.
+ *
+ * \copyright
+ * Copyright (c) 2012-2016, OpenGeoSys Community (http://www.opengeosys.org)
+ * Distributed under a Modified BSD License.
+ * See accompanying file LICENSE.txt or
+ * http://www.opengeosys.org/project/license
+ *
+ * \file DimensionLessGibbsFreeEnergyRegion1.h
+ *
+ * Created on December 8, 2016, 12:31 PM
+ */
+
+#ifndef OGS_DIMENSION_LESS_GIBBS_FREE_ENERGY_REGION1_H
+#define OGS_DIMENSION_LESS_GIBBS_FREE_ENERGY_REGION1_H
+
+namespace MaterialLib
+{
+namespace Fluid
+{
+/**
+ * A class for dimensionless Gibbs free energy defined by
+ * \f[
+ * \gamma=\sum_{i=1}^{34}\left[
+ * n_i * (7.1-\pi)^{l_i}(\tau - 1.222)^{j_i}
+ * \right]
+ * \f]
+ * <a href="http://www.iapws.org/relguide/IF97-Rev.pdf">IF97-Rev</a>
+ *
+ * Coefficients \f$n_i\f$, \f$j_i\f$ and \f$l_i\f$ are given in three static
+ * arrays in the cpp file.
+ */
+class DimensionLessGibbsFreeEnergyRegion1
+{
+public:
+ DimensionLessGibbsFreeEnergyRegion1() = default;
+
+ /**
+ * Get the value
+ * @param pi Dimension less temperature
+ * @param tau Dimension less pressure
+ * @return The value
+ */
+ double get_gamma(const double tau, const double pi) const;
+
+ /**
+ * Get the 1st order partial derivative of the dimension less Gibbs free
+ * energy with respect to dimension less temperature, tau
+ *
+ * @param pi Dimension less temperature
+ * @param tau Dimension less pressure
+ * @return The value
+ */
+ double get_dgamma_dtau(const double tau, const double pi) const;
+
+ /**
+ * Get the 2nd order partial derivative of the dimension less Gibbs free
+ * energy with respect to dimension less temperature, tau
+ *
+ * @param pi Dimension less temperature
+ * @param tau Dimension less pressure
+ * @return The value
+ */
+ double get_dgamma_dtau_dtau(const double tau, const double pi) const;
+
+ /**
+ * Get the 1st order partial derivative of the dimension less Gibbs free
+ * energy with respect to dimension less pressure, pi
+ *
+ * @param pi Dimension less temperature
+ * @param tau Dimension less pressure
+ * @return The value
+ */
+ double get_dgamma_dpi(const double tau, const double pi) const;
+
+ /**
+ * Get the 2nd order partial derivative of the dimension less Gibbs free
+ * energy with respect to dimension less pressure, pi
+ *
+ * @param pi Dimension less temperature
+ * @param tau Dimension less pressure
+ * @return The value
+ */
+ double get_dgamma_dpi_dpi(const double tau, const double pi) const;
+
+ /**
+ * Get the 2nd order partial derivative of the dimension less Gibbs free
+ * energy with respect to dimension less temperature, tau, and dimension
+ * less pressure, pi
+ * @param pi Dimension less temperature
+ * @param tau Dimension less pressure
+ * @return The value
+ */
+ double get_dgamma_dtau_dpi(const double tau, const double pi) const;
+};
+
+} // end namespace
+} // end namespace
+#endif /* OGS_DIMENSION_LESS_GIBBS_FREE_ENERGY_REGION1_H */
diff --git a/Tests/MaterialLib/TestDimensionLessGibbsFreeEnergy.cpp b/Tests/MaterialLib/TestDimensionLessGibbsFreeEnergy.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..81473113bb9ff0a75e853c7425b03ee6d6224fe8
--- /dev/null
+++ b/Tests/MaterialLib/TestDimensionLessGibbsFreeEnergy.cpp
@@ -0,0 +1,40 @@
+/**
+ * \copyright
+ * Copyright (c) 2012-2016, OpenGeoSys Community (http://www.opengeosys.org)
+ * Distributed under a Modified BSD License.
+ * See accompanying file LICENSE.txt or
+ * http://www.opengeosys.org/project/license
+ *
+ * \file TestDimensionLessGibbsFreeEnergy.cpp
+ *
+ * Created on December 9, 2016, 12:31 PM
+ */
+#include <gtest/gtest.h>
+
+#include <memory>
+
+#include "Tests/TestTools.h"
+
+#include "MaterialLib/Fluid/GibbsFreeEnergy/DimensionLessGibbsFreeEnergyRegion1.h"
+
+using namespace MaterialLib;
+using namespace MaterialLib::Fluid;
+
+TEST(MaterialGibbsFreeEnergy, checkDimensionLessGibbsFreeEnergyRegion1)
+{
+ DimensionLessGibbsFreeEnergyRegion1 gfeR1;
+ const double T = 473.15;
+ const double p = 4.e+7;
+ const double T_ref = 1386;
+ const double p_ref = 1.653e+7;
+
+ const double tau = T_ref / T;
+ const double pi = p / p_ref;
+
+ ASSERT_NEAR(-0.946316961309, gfeR1.get_gamma(tau, pi), 1.e-10);
+ ASSERT_NEAR(0.0849626110088, gfeR1.get_dgamma_dpi(tau, pi), 1.e-10);
+ ASSERT_NEAR(1.360259836187, gfeR1.get_dgamma_dtau(tau, pi), 1.e-10);
+ ASSERT_NEAR(-9.726737889528e-4, gfeR1.get_dgamma_dpi_dpi(tau, pi), 1.e-10);
+ ASSERT_NEAR(-1.089765627732, gfeR1.get_dgamma_dtau_dtau(tau, pi), 1.e-10);
+ ASSERT_NEAR(0.013153993854, gfeR1.get_dgamma_dtau_dpi(tau, pi), 1.e-10);
+}