diff --git a/include/RI/physics/GW.h b/include/RI/physics/GW.h
new file mode 100644
index 0000000..00643e7
--- /dev/null
+++ b/include/RI/physics/GW.h
@@ -0,0 +1,69 @@
+// ===================
+//  Author: Minye Zhang, almost completely copied from Exx.h
+//  date: 2022.12.18
+// ===================
+
+#pragma once
+
+// #include "Exx_Post_2D.h"
+#include "../global/Global_Func-2.h"
+#include "../global/Tensor.h"
+#include "../ri/LRI.h"
+
+#include <mpi.h>
+#include <array>
+#include <map>
+
+namespace RI
+{
+
+//! class to compute the correlation self-energy in G0W0 approximation by space-time method
+template<typename TA, typename Tcell, std::size_t Ndim, typename Tdata>
+class G0W0
+{
+public:
+	using TC = std::array<Tcell,Ndim>;
+	using TAC = std::pair<TA,TC>;
+	using Tdata_real = Global_Func::To_Real_t<Tdata>;
+	constexpr static std::size_t Npos = Ndim;		// tmp
+	using Tatom_pos = std::array<double,Npos>;		// tmp
+
+	void set_parallel(
+		const MPI_Comm &mpi_comm,
+		const std::map<TA,Tatom_pos> &atoms_pos,
+		const std::array<Tatom_pos,Ndim> &latvec,
+		const std::array<Tcell,Ndim> &period);
+
+	void set_Cs(
+		const std::map<TA, std::map<TAC, Tensor<Tdata>>> &Cs,
+		const Tdata_real &threshold_C);
+	void set_csm_threshold(
+		const Tdata_real &threshold) { this->lri.csm.set_threshold(threshold); }
+
+	void cal_Sigc(
+		const std::map<TA, std::map<TAC, Tensor<Tdata>>> gf_tau,
+		const Tdata_real &threshold_G,
+		const std::map<TA, std::map<TAC, Tensor<Tdata>>> Wc_tau,
+		const Tdata_real &threshold_W);
+
+	std::map<TA, std::map<TAC, Tensor<Tdata>>> Sigc_tau;
+
+public:
+	LRI<TA,Tcell,Ndim,Tdata> lri;
+
+	struct Flag_Finish
+	{
+		bool stru=false;
+		bool C=false;
+	};
+	Flag_Finish flag_finish;
+
+	MPI_Comm mpi_comm;
+	std::map<TA,Tatom_pos> atoms_pos;
+	std::array<Tatom_pos,Ndim> latvec;
+	std::array<Tcell,Ndim> period;	
+};
+
+}
+
+#include "GW.hpp"
\ No newline at end of file
diff --git a/include/RI/physics/GW.hpp b/include/RI/physics/GW.hpp
new file mode 100644
index 0000000..1d6cac9
--- /dev/null
+++ b/include/RI/physics/GW.hpp
@@ -0,0 +1,71 @@
+// ===================
+//  Author: Minye Zhang, almost completely copied from Exx.hpp
+//  date: 2022.12.18
+// ===================
+#pragma once
+
+#include "GW.h"
+#include "../ri/Label.h"
+
+namespace RI
+{
+
+template<typename TA, typename Tcell, std::size_t Ndim, typename Tdata>
+void G0W0<TA,Tcell,Ndim,Tdata>::set_parallel(
+	const MPI_Comm &mpi_comm_in,
+	const std::map<TA,Tatom_pos> &atoms_pos_in,
+	const std::array<Tatom_pos,Ndim> &latvec_in,
+	const std::array<Tcell,Ndim> &period_in)
+{
+	this->mpi_comm = mpi_comm_in;
+	this->atoms_pos = atoms_pos_in;
+	this->latvec = latvec_in;
+	this->period = period_in;
+
+	this->lri.set_parallel(this->mpi_comm, this->atoms_pos, this->latvec, this->period);
+	this->flag_finish.stru = true;
+	//if()
+		// this->post_2D.set_parallel(this->mpi_comm, this->atoms_pos, this->period);
+}
+
+template<typename TA, typename Tcell, std::size_t Ndim, typename Tdata>
+void G0W0<TA,Tcell,Ndim,Tdata>::set_Cs(
+	const std::map<TA, std::map<TAC, Tensor<Tdata>>> &Cs,
+	const Tdata_real &threshold_C)
+{
+	this->lri.set_tensors_map2( Cs, Label::ab::a, threshold_C );
+	this->lri.set_tensors_map2( Cs, Label::ab::b, threshold_C );
+	this->flag_finish.C = true;
+}
+
+
+template <typename TA, typename Tcell, std::size_t Ndim, typename Tdata>
+void G0W0<TA, Tcell, Ndim, Tdata>::cal_Sigc(
+	const std::map<TA, std::map<TAC, Tensor<Tdata>>> gf_tau,
+	const Tdata_real &threshold_G,
+	const std::map<TA, std::map<TAC, Tensor<Tdata>>> Wc_tau,
+	const Tdata_real &threshold_W)
+{
+	assert(this->flag_finish.stru);
+	assert(this->flag_finish.C);
+	// setup Green's function
+	this->lri.set_tensors_map2( gf_tau, Label::ab::a1b1, threshold_G );
+	this->lri.set_tensors_map2( gf_tau, Label::ab::a1b2, threshold_G );
+	this->lri.set_tensors_map2( gf_tau, Label::ab::a2b1, threshold_G );
+	this->lri.set_tensors_map2( gf_tau, Label::ab::a2b2, threshold_G );
+
+	// setup screened Coulomb interaction
+	this->lri.set_tensors_map2( Wc_tau, Label::ab::a0b0, threshold_W );
+
+	std::vector<std::map<TA, std::map<TAC, Tensor<Tdata>>>> Sigc_vec(1);
+	this->lri.coefficients = {nullptr};
+	this->lri.cal(
+		{Label::ab_ab::a0b0_a1b1,
+		 Label::ab_ab::a0b0_a1b2,
+		 Label::ab_ab::a0b0_a2b1,
+		 Label::ab_ab::a0b0_a2b2},
+		Sigc_vec);
+	this->Sigc_tau = std::move(Sigc_vec[0]);
+}
+
+} // namespace RI
\ No newline at end of file
diff --git a/unittests/physics/GW-test.hpp b/unittests/physics/GW-test.hpp
new file mode 100644
index 0000000..336ce8a
--- /dev/null
+++ b/unittests/physics/GW-test.hpp
@@ -0,0 +1,27 @@
+// ===================
+//  Author: Minye Zhang, almost copied from Exx-test.hpp
+//  date: 2022.06.02
+// ===================
+
+#pragma once
+
+#include "RI/physics/GW.h"
+// #include <complex>
+
+namespace GW_Test
+{
+	template<typename Tdata>
+	void main(int argc, char *argv[])
+	{
+		int mpi_init_provide;
+		MPI_Init_thread(&argc, &argv, MPI_THREAD_MULTIPLE, &mpi_init_provide);
+
+		RI::G0W0<int,int,1,Tdata> g0w0;
+		g0w0.set_parallel(MPI_COMM_WORLD, {{1,{0}},{2,{4}}}, {}, {1});
+		g0w0.set_csm_threshold(1E-4);
+		g0w0.set_Cs({}, 1E-4);
+		g0w0.cal_Sigc({}, 1E-4, {}, 1E-4);
+
+		MPI_Finalize();
+	}
+}
\ No newline at end of file