diff --git a/python/wrap/model.cpp b/python/wrap/model.cpp
index 3f4a636..1b5b106 100644
--- a/python/wrap/model.cpp
+++ b/python/wrap/model.cpp
@@ -1,508 +1,516 @@
 /*
  *  SPDX-License-Indentifier: AGPL-3.0-or-later
  *
  *  Copyright (©) 2016-2022 EPFL (École Polytechnique Fédérale de Lausanne),
  *  Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
  *
  *  This program is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU Affero General Public License as published
  *  by the Free Software Foundation, either version 3 of the License, or
  *  (at your option) any later version.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU Affero General Public License for more details.
  *
  *  You should have received a copy of the GNU Affero General Public License
  *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
  *
  */
 /* -------------------------------------------------------------------------- */
 #include "model.hh"
 #include "adhesion_functional.hh"
+#include "elastic_functional.hh"
 #include "functional.hh"
 #include "integral_operator.hh"
 #include "model_dumper.hh"
 #include "model_extensions.hh"
 #include "model_factory.hh"
 #include "numpy.hh"
 #include "residual.hh"
 #include "wrap.hh"
 #include <pybind11/stl.h>
 /* -------------------------------------------------------------------------- */
 
 namespace tamaas {
 
 namespace wrap {
 
 using namespace py::literals;
 
 struct model_operator_accessor {
   Model& m;
 
   decltype(auto) get(const std::string& name) {
     return m.getIntegralOperator(name);
   }
 };
 
 /// Wrap functional classes
 void wrapFunctionals(py::module& mod) {
   py::class_<functional::Functional, std::shared_ptr<functional::Functional>,
              functional::wrap::PyFunctional>
       func(mod, "Functional");
   func.def(py::init<>())
       .def("computeF", &functional::Functional::computeF,
            "Compute functional value")
       .def("computeGradF", &functional::Functional::computeGradF,
            "Compute functional gradient");
 
+  py::class_<functional::ElasticFunctionalPressure>(
+      mod, "ElasticFunctionalPressure", func)
+      .def(py::init<const IntegralOperator&, const GridBase<Real>&>());
+  py::class_<functional::ElasticFunctionalGap>(mod, "ElasticFunctionalGap",
+                                               func)
+      .def(py::init<const IntegralOperator&, const GridBase<Real>&>());
+
   py::class_<functional::AdhesionFunctional> adh(mod, "AdhesionFunctional",
                                                  func);
   adh.def_property("parameters", &functional::AdhesionFunctional::getParameters,
                    &functional::AdhesionFunctional::setParameters,
                    "Parameters dictionary")
       .def("setParameters", [](functional::AdhesionFunctional& f,
                                const std::map<std::string, Real>& m) {
         TAMAAS_DEPRECATE("setParameters()", "the parameters property");
         f.setParameters(m);
       });
 
   py::class_<functional::ExponentialAdhesionFunctional>(
       mod, "ExponentialAdhesionFunctional", adh,
       "Potential of the form F = -γ·exp(-g/ρ)")
       .def(py::init<const GridBase<Real>&>(), "surface"_a);
   py::class_<functional::MaugisAdhesionFunctional>(
       mod, "MaugisAdhesionFunctional", adh,
       "Cohesive zone potential F = H(g - ρ)·γ/ρ")
       .def(py::init<const GridBase<Real>&>(), "surface"_a);
   py::class_<functional::SquaredExponentialAdhesionFunctional>(
       mod, "SquaredExponentialAdhesionFunctional", adh,
       "Potential of the form F = -γ·exp(-0.5·(g/ρ)²)")
       .def(py::init<const GridBase<Real>&>(), "surface"_a);
 }
 
 template <typename T>
 std::unique_ptr<GridBase<T>> instanciateFromNumpy(numpy<T>& num) {
   std::unique_ptr<GridBase<T>> result = nullptr;
 
   switch (num.ndim()) {
   case 2:
     result = std::make_unique<GridNumpy<Grid<T, 1>>>(num);
     return result;
   case 3:
     result = std::make_unique<GridNumpy<Grid<T, 2>>>(num);
     return result;
   case 4:
     result = std::make_unique<GridNumpy<Grid<T, 3>>>(num);
     return result;
   default:
     TAMAAS_EXCEPTION("instanciateFromNumpy expects the last dimension of numpy "
                      "array to be the number of components");
   }
 }
 
 /// Wrap IntegralOperator
 void wrapIntegralOperator(py::module& mod) {
   py::class_<IntegralOperator>(mod, "IntegralOperator")
       .def("apply",
            [](IntegralOperator& op, numpy<Real> input, numpy<Real> output) {
              TAMAAS_DEPRECATE("apply()", "the () operator");
              auto in = instanciateFromNumpy(input);
              auto out = instanciateFromNumpy(output);
 
              op.apply(*in, *out);
            })
       .def(TAMAAS_DEPRECATE_ACCESSOR(getModel, IntegralOperator, "model"),
            py::return_value_policy::reference)
       .def(TAMAAS_DEPRECATE_ACCESSOR(getKind, IntegralOperator, "kind"))
       .def(TAMAAS_DEPRECATE_ACCESSOR(getType, IntegralOperator, "type"))
 
       .def(
           "__call__",
           [](IntegralOperator& op, numpy<Real> input, numpy<Real> output) {
             auto in = instanciateFromNumpy(input);
             auto out = instanciateFromNumpy(output);
 
             op.apply(*in, *out);
           },
           "Apply the integral operator")
       .def("updateFromModel", &IntegralOperator::updateFromModel,
            "Resets internal persistent variables from the model")
 
       .def_property_readonly("kind", &IntegralOperator::getKind)
       .def_property_readonly("model", &IntegralOperator::getModel)
       .def_property_readonly("type", &IntegralOperator::getType)
       .def_property_readonly("shape", &IntegralOperator::matvecShape)
       .def(
           "matvec",
           [](const IntegralOperator& op, numpy<Real> X) -> GridBase<Real> {
             GridBaseNumpy<Real> x(X);
             auto y = op.matvec(x);
             return y;
           },
           py::return_value_policy::move);
 
   py::enum_<integration_method>(mod, "integration_method",
                                 "Integration method used for the computation "
                                 "of volumetric Fourier operators")
       .value("linear", integration_method::linear,
              "No approximation error, O(N₁·N₂·N₃) time complexity, may cause "
              "float overflow/underflow")
       .value("cutoff", integration_method::cutoff,
              "Approximation, O(sqrt(N₁²+N₂²)·N₃²) time complexity, no "
              "overflow/underflow risk");
 }
 
 /// Wrap BEEngine classes
 void wrapBEEngine(py::module& mod) {
   py::class_<BEEngine>(mod, "BEEngine")
       .def("solveNeumann", &BEEngine::solveNeumann)
       .def("solveDirichlet", &BEEngine::solveDirichlet)
       .def("registerNeumann", &BEEngine::registerNeumann)
       .def("registerDirichlet", &BEEngine::registerDirichlet)
       .def(TAMAAS_DEPRECATE_ACCESSOR(getModel, BEEngine, "model"),
            py::return_value_policy::reference)
 
       .def_property_readonly("model", &BEEngine::getModel);
 }
 
 template <model_type type>
 void wrapModelTypeTrait(py::module& mod) {
   using trait = model_type_traits<type>;
   py::class_<trait>(mod, trait::repr)
       .def_property_readonly_static(
           "dimension", [](py::object) { return trait::dimension; },
           "Dimension of computational domain")
       .def_property_readonly_static(
           "components", [](py::object) { return trait::components; },
           "Number of components of vector fields")
       .def_property_readonly_static(
           "boundary_dimension",
           [](py::object) { return trait::boundary_dimension; },
           "Dimension of boundary of computational domain")
       .def_property_readonly_static(
           "voigt", [](py::object) { return trait::voigt; },
           "Number of components of symmetrical tensor fields")
       .def_property_readonly_static("indices",
                                     [](py::object) { return trait::indices; });
 }
 
 /// Wrap Models
 void wrapModelClass(py::module& mod) {
   py::enum_<model_type>(mod, "model_type")
       .value("basic_1d", model_type::basic_1d,
              "Normal contact with 1D interface")
       .value("basic_2d", model_type::basic_2d,
              "Normal contact with 2D interface")
       .value("surface_1d", model_type::surface_1d,
              "Normal & tangential contact with 1D interface")
       .value("surface_2d", model_type::surface_2d,
              "Normal & tangential contact with 2D interface")
       .value("volume_1d", model_type::volume_1d,
              "Contact with volumetric representation and 1D interface")
       .value("volume_2d", model_type::volume_2d,
              "Contact with volumetric representation and 2D interface");
 
   auto trait_mod = mod.def_submodule("_type_traits");
   wrapModelTypeTrait<model_type::basic_1d>(trait_mod);
   wrapModelTypeTrait<model_type::surface_1d>(trait_mod);
   wrapModelTypeTrait<model_type::volume_1d>(trait_mod);
   wrapModelTypeTrait<model_type::basic_2d>(trait_mod);
   wrapModelTypeTrait<model_type::surface_2d>(trait_mod);
   wrapModelTypeTrait<model_type::volume_2d>(trait_mod);
 
   py::class_<model_operator_accessor>(mod, "_model_operator_acessor")
       .def(py::init<Model&>())
       .def(
           "__getitem__",
           [](model_operator_accessor& acc, std::string name) {
             try {
               return acc.get(name);
             } catch (std::out_of_range&) {
               throw py::key_error(name);
             }
           },
           py::return_value_policy::reference_internal)
       .def("__contains__",
            [](model_operator_accessor& acc, std::string key) {
              const auto ops = acc.m.getIntegralOperators();
              return std::find(ops.begin(), ops.end(), key) != ops.end();
            })
       .def(
           "__iter__",
           [](const model_operator_accessor& acc) {
             const auto& ops = acc.m.getIntegralOperatorsMap();
             return py::make_key_iterator(ops.cbegin(), ops.cend());
           },
           py::keep_alive<0, 1>());
 
   py::class_<Model>(mod, "Model")
       .def(py::init(py::overload_cast<model_type, const std::vector<Real>&,
                                       const std::vector<UInt>&>(
           &ModelFactory::createModel)))
       .def_property_readonly("type", &Model::getType)
       .def_property("E", &Model::getYoungModulus, &Model::setYoungModulus,
                     "Young's modulus")
       .def_property("nu", &Model::getPoissonRatio, &Model::setPoissonRatio,
                     "Poisson's ratio")
       .def_property_readonly("mu", &Model::getShearModulus, "Shear modulus")
       .def_property_readonly("E_star", &Model::getHertzModulus,
                              "Contact (Hertz) modulus")
       .def_property_readonly("be_engine", &Model::getBEEngine,
                              "Boundary element engine")
 
       .def(
           "setElasticity",
           [](Model& m, Real E, Real nu) {
             TAMAAS_DEPRECATE("setElasticity()", "the E and nu properties");
             m.setElasticity(E, nu);
           },
           "E"_a, "nu"_a)
       .def(TAMAAS_DEPRECATE_ACCESSOR(getHertzModulus, Model, "E_star"))
       .def(TAMAAS_DEPRECATE_ACCESSOR(getYoungModulus, Model, "E"))
       .def(TAMAAS_DEPRECATE_ACCESSOR(getShearModulus, Model, "mu"))
       .def(TAMAAS_DEPRECATE_ACCESSOR(getPoissonRatio, Model, "nu"))
       .def(TAMAAS_DEPRECATE_ACCESSOR(getTraction, Model, "traction"),
            py::return_value_policy::reference_internal)
       .def(TAMAAS_DEPRECATE_ACCESSOR(getDisplacement, Model, "displacement"),
            py::return_value_policy::reference_internal)
       .def(TAMAAS_DEPRECATE_ACCESSOR(getSystemSize, Model, "system_size"))
       .def(TAMAAS_DEPRECATE_ACCESSOR(getDiscretization, Model, "shape"))
       .def(TAMAAS_DEPRECATE_ACCESSOR(getBoundarySystemSize, Model,
                                      "boundary_system_size"))
       .def(TAMAAS_DEPRECATE_ACCESSOR(getBoundaryDiscretization, Model,
                                      "boundary_shape"))
 
       .def("solveNeumann", &Model::solveNeumann,
            "Solve surface tractions -> displacements")
       .def("solveDirichlet", &Model::solveDirichlet,
            "Solve surface displacemnts -> tractions")
       .def("dump", &Model::dump, "Write model data to registered dumpers")
       .def("addDumper", &Model::addDumper, "dumper"_a, py::keep_alive<1, 2>(),
            "Register a dumper")
 
       .def(
           "getBEEngine",
           [](Model& m) -> decltype(m.getBEEngine()) {
             TAMAAS_DEPRECATE("getBEEngine()", "the be_engine property");
             return m.getBEEngine();
           },
           py::return_value_policy::reference_internal)
       .def(
           "getIntegralOperator",
           [](const Model& m, std::string name) {
             TAMAAS_DEPRECATE("getIntegralOperator()", "the operators property");
             return m.getIntegralOperator(name);
           },
           "operator_name"_a, py::return_value_policy::reference_internal)
       .def(
           "registerField",
           [](Model& m, std::string name, numpy<Real> field) {
             TAMAAS_DEPRECATE("registerField()", "the [] operator");
             auto f = instanciateFromNumpy(field);
             m.registerField(name, std::move(f));
           },
           "field_name"_a, "field"_a, py::keep_alive<1, 3>())
       .def(
           "getField",
           [](const Model& m, std::string name) -> decltype(m.getField(name)) {
             TAMAAS_DEPRECATE("getField()", "the [] operator");
             return m.getField(name);
           },
           "field_name"_a, py::return_value_policy::reference_internal)
       .def(
           "getFields",
           [](const Model& m) {
             TAMAAS_DEPRECATE("getFields()", "list(model)");
             return m.getFields();
           },
           "Return fields list")
 
       .def(
           "applyElasticity",
           [](Model& model, numpy<Real> stress, numpy<Real> strain) {
             auto out = instanciateFromNumpy(stress);
             auto in = instanciateFromNumpy(strain);
 
             model.applyElasticity(*out, *in);
           },
           "Apply Hooke's law")
 
       // Python magic functions
       .def("__repr__",
            [](const Model& m) {
              std::stringstream ss;
              ss << m;
              return ss.str();
            })
       .def(
           "__getitem__",
           [](const Model& m, std::string key) -> decltype(m[key]) {
             try {
               return m[key];
             } catch (std::out_of_range&) {
               throw py::key_error(key);
             }
           },
           py::return_value_policy::reference_internal, "Get field")
       .def(
           "__setitem__",
           [](Model& m, std::string name, numpy<Real> field) {
             auto f = instanciateFromNumpy(field);
             m.registerField(name, std::move(f));
           },
           py::keep_alive<1, 3>(), "Register new field")
       .def(
           "__contains__",
           [](const Model& m, std::string key) {
             const auto fields = m.getFields();
             return std::find(fields.begin(), fields.end(), key) != fields.end();
           },
           py::keep_alive<0, 1>(), "Test field existence")
       .def(
           "__iter__",
           [](const Model& m) {
             const auto& fields = m.getFieldsMap();
             return py::make_key_iterator(fields.cbegin(), fields.cend());
           },
           py::keep_alive<0, 1>(), "Iterator on fields")
       .def(
           "__copy__",
           [](const Model&) {
             throw std::runtime_error("__copy__ not implemented");
           },
           "Shallow copy of model. Not implemented.")
       .def(
           "__deepcopy__",
           [](const Model& m, py::dict) { return ModelFactory::createModel(m); },
           "Deep copy of model.")
       .def_property_readonly("boundary_fields", &Model::getBoundaryFields)
       .def_property_readonly(
           "operators", [](Model& m) { return model_operator_accessor{m}; },
           "Returns a dict-like object allowing access to the model's "
           "integral "
           "operators")
       // More python-like access to model properties
       .def_property_readonly("shape", &Model::getDiscretization,
                              "Discretization (local in MPI environment)")
       .def_property_readonly("global_shape", &Model::getGlobalDiscretization,
                              "Global discretization (in MPI environement)")
       .def_property_readonly("boundary_shape",
                              &Model::getBoundaryDiscretization,
                              "Number of points on boundary")
       .def_property_readonly("system_size", &Model::getSystemSize,
                              "Size of physical domain")
       .def_property_readonly("boundary_system_size",
                              &Model::getBoundarySystemSize,
                              "Physical size of surface")
       .def_property_readonly("traction",
                              (const GridBase<Real>& (Model::*)() const) &
                                  Model::getTraction,
                              "Surface traction field")
       .def_property_readonly("displacement",
                              (const GridBase<Real>& (Model::*)() const) &
                                  Model::getDisplacement,
                              "Displacement field");
 
   py::class_<ModelDumper, PyModelDumper, std::shared_ptr<ModelDumper>>(
       mod, "ModelDumper")
       .def(py::init<>())
       .def("dump", &ModelDumper::dump, "model"_a, "Dump model")
       .def(
           "__lshift__",
           [](ModelDumper& dumper, Model& model) { dumper << model; },
           "Dump model");
 }
 
 /// Wrap factory for models
 void wrapModelFactory(py::module& mod) {
   py::class_<ModelFactory>(mod, "ModelFactory")
       .def_static(
           "createModel",
           py::overload_cast<model_type, const std::vector<Real>&,
                             const std::vector<UInt>&>(
               &ModelFactory::createModel),
           "model_type"_a, "system_size"_a, "global_discretization"_a,
           R"-(Create a new model of a given type, physical size and *global*
 discretization.
 
 :param model_type: the type of desired model
 :param system_size: the physical size of the domain in each direction
 :param global_discretization: number of points in each direction)-")
       .def_static("createModel",
                   py::overload_cast<const Model&>(&ModelFactory::createModel),
                   "model"_a, "Create a deep copy of a model.")
       .def_static("createResidual", &ModelFactory::createResidual, "model"_a,
                   "sigma_y"_a, "hardening"_a = 0.,
                   R"-(Create an isotropic linear hardening residual.
 :param model: the model on which to define the residual
 :param sigma_y: the (von Mises) yield stress
 :param hardening: the hardening modulus)-")
       .def_static("registerVolumeOperators",
                   &ModelFactory::registerVolumeOperators, "model"_a,
                   "Register Boussinesq and Mindlin operators to model.");
 }
 
 /// Wrap residual class
 void wrapResidual(py::module& mod) {
   // TODO adapt to n-dim
   py::class_<Residual, PyResidual>(mod, "Residual")
       .def(py::init<Model*>())
       .def("computeResidual",
            [](Residual& res, numpy<Real>& x) {
              auto in = instanciateFromNumpy(x);
              res.computeResidual(*in);
            })
       .def("computeStress",
            [](Residual& res, numpy<Real>& x) {
              auto in = instanciateFromNumpy(x);
              res.computeStress(*in);
            })
       .def("updateState",
            [](Residual& res, numpy<Real>& x) {
              auto in = instanciateFromNumpy(x);
              res.updateState(*in);
            })
       .def("computeResidualDisplacement",
            [](Residual& res, numpy<Real>& x) {
              auto in = instanciateFromNumpy(x);
              res.computeResidualDisplacement(*in);
            })
       .def(
           "applyTangent",
           [](Residual& res, numpy<Real>& output, numpy<Real>& input,
              numpy<Real>& current_strain_inc) {
             auto out = instanciateFromNumpy(output);
             auto in = instanciateFromNumpy(input);
             auto inc = instanciateFromNumpy(current_strain_inc);
             res.applyTangent(*out, *in, *inc);
           },
           "output"_a, "input"_a, "current_strain_increment"_a)
       .def("getVector", &Residual::getVector,
            py::return_value_policy::reference_internal)
       .def("getPlasticStrain", &Residual::getPlasticStrain,
            py::return_value_policy::reference_internal)
       .def("getStress", &Residual::getStress,
            py::return_value_policy::reference_internal)
       .def("setIntegrationMethod", &Residual::setIntegrationMethod, "method"_a,
            "cutoff"_a = 1e-12)
       .def_property("yield_stress", &Residual::getYieldStress,
                     &Residual::setYieldStress)
       .def_property("hardening_modulus", &Residual::getHardeningModulus,
                     &Residual::setHardeningModulus)
       .def_property_readonly("model", &Residual::getModel);
 }
 
 void wrapModel(py::module& mod) {
   wrapBEEngine(mod);
   wrapModelClass(mod);
   wrapModelFactory(mod);
   wrapFunctionals(mod);
   wrapResidual(mod);
   wrapIntegralOperator(mod);
 }
 
 }  // namespace wrap
 
 }  // namespace tamaas
diff --git a/src/model/elastic_functional.hh b/src/model/elastic_functional.hh
index a73cea1..031c8a3 100644
--- a/src/model/elastic_functional.hh
+++ b/src/model/elastic_functional.hh
@@ -1,79 +1,80 @@
 /*
  *  SPDX-License-Indentifier: AGPL-3.0-or-later
  *
  *  Copyright (©) 2016-2022 EPFL (École Polytechnique Fédérale de Lausanne),
  *  Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
  *
  *  This program is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU Affero General Public License as published
  *  by the Free Software Foundation, either version 3 of the License, or
  *  (at your option) any later version.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU Affero General Public License for more details.
  *
  *  You should have received a copy of the GNU Affero General Public License
  *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
  *
  */
 /* -------------------------------------------------------------------------- */
 #ifndef ELASTIC_FUNCTIONAL_HH
 #define ELASTIC_FUNCTIONAL_HH
 /* -------------------------------------------------------------------------- */
 #include "functional.hh"
 #include "model.hh"
 #include "tamaas.hh"
 /* -------------------------------------------------------------------------- */
 namespace tamaas {
 
 namespace functional {
 
 /// Generic functional for elastic energy
 class ElasticFunctional : public Functional {
 public:
   ElasticFunctional(const IntegralOperator& op, const GridBase<Real>& surface)
-      : op(op), surface(surface) {
+      : op(op), surface() {
+    this->surface.wrap(surface);
     const Model& model = op.getModel();
     buffer = allocateGrid<true, Real>(op.getType(),
                                       model.getBoundaryDiscretization());
   }
 
 protected:
   const IntegralOperator& op;
-  const GridBase<Real>& surface;
+  GridBase<Real> surface;
   std::unique_ptr<GridBase<Real>> mutable buffer;
 };
 
 /* -------------------------------------------------------------------------- */
 
 /// Functional with pressure as primal field
 class ElasticFunctionalPressure : public ElasticFunctional {
 public:
   using ElasticFunctional::ElasticFunctional;
   /// Compute functional with input pressure
   Real computeF(GridBase<Real>& pressure, GridBase<Real>& dual) const override;
   /// Compute functional gradient with input pressure
   void computeGradF(GridBase<Real>& pressure,
                     GridBase<Real>& gradient) const override;
 };
 
 /* -------------------------------------------------------------------------- */
 
 /// Functional with gap as primal field
 class ElasticFunctionalGap : public ElasticFunctional {
 public:
   using ElasticFunctional::ElasticFunctional;
   /// Compute functional with input gap
   Real computeF(GridBase<Real>& gap, GridBase<Real>& dual) const override;
   /// Compute functional gradient with input gap
   void computeGradF(GridBase<Real>& gap,
                     GridBase<Real>& gradient) const override;
 };
 
 }  // namespace functional
 
 }  // namespace tamaas
 /* -------------------------------------------------------------------------- */
 #endif  // ELASTIC_FUNCTIONAL_HH