diff --git a/.clangd b/.clangd
new file mode 100644
index 000000000..c7c821813
--- /dev/null
+++ b/.clangd
@@ -0,0 +1,3 @@
+CompileFlags: # Tweak the parse settings, example directory given to show format
+  Add:
+    - "-I./include"
diff --git a/.github/workflows/build_test.yml b/.github/workflows/build_test.yml
index 94621c9ca..a42cf57c5 100644
--- a/.github/workflows/build_test.yml
+++ b/.github/workflows/build_test.yml
@@ -6,6 +6,7 @@ on:
   pull_request:
     branches: ["main"]
     tags: "v*"
+  workflow_dispatch:
 env:
   BUILD_TYPE: Release
   CPM_SOURCE_CACHE: ${{github.workspace}}/cache/cpm
diff --git a/.gitignore b/.gitignore
index 57b9e1e6e..f909ee667 100644
--- a/.gitignore
+++ b/.gitignore
@@ -45,3 +45,5 @@ coverage/
 *.cube
 *.pgrid
 *.ply
+.direnv
+.envrc
diff --git a/3rdparty/CMakeLists.txt b/3rdparty/CMakeLists.txt
index f8f7a9bb1..5d1093751 100644
--- a/3rdparty/CMakeLists.txt
+++ b/3rdparty/CMakeLists.txt
@@ -1,5 +1,6 @@
 set(CMAKE_UNITY_BUILD OFF)
 
+if (NOT NIX_BUILD)
 CPMAddPackage(
     NAME fmt
     GITHUB_REPOSITORY "fmtlib/fmt"
@@ -14,6 +15,8 @@ CPMAddPackage(
     VERSION "1.x"
 )
 
+endif ()
+
 if(NOT "${USE_SYSTEM_TBB}")
 
 set(TBB_OPTIONS "")
@@ -30,7 +33,7 @@ endif()
 if(WIN32 AND CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     list(APPEND TBB_OPTIONS "CMAKE_CXX_FLAGS=-O2 -fno-stack-clash-protection -fno-fcf-protection")
 endif()
-
+if (NOT NIX_BUILD)
 CPMAddPackage(
     NAME oneTBB
     GITHUB_REPOSITORY "uxlfoundation/oneTBB"
@@ -38,7 +41,9 @@ CPMAddPackage(
     OPTIONS ${TBB_OPTIONS}
 )
 endif()
+endif()
 
+if (NOT NIX_BUILD)
 CPMAddPackage(
     NAME unordered_dense
     GITHUB_REPOSITORY "martinus/unordered_dense"
@@ -59,6 +64,7 @@ CPMAddPackage(
     VERSION "2.4.2"
 )
 
+endif()
 if("${USE_MLX}")
 CPMAddPackage(
     NAME mlx
@@ -66,12 +72,13 @@ CPMAddPackage(
     VERSION "0.6.0"
 )
 else()
+if (NOT NIX_BUILD)
 CPMAddPackage(
     NAME "nlohmann_json"
     GITHUB_REPOSITORY "nlohmann/json"
     VERSION "3.11.3"
 )
-
+endif()
 endif()
 
 if(NOT "${USE_SYSTEM_EIGEN}")
@@ -88,7 +95,7 @@ if("${eigen3_ADDED}")
 endif()
 
 endif()
-
+if (NOT NIX_BUILD)
 CPMAddPackage(
     NAME gemmi
     GITHUB_REPOSITORY project-gemmi/gemmi
@@ -122,7 +129,7 @@ if("${LBFGSpp_ADDED}")
     add_library(LBFGSpp::LBFGSpp INTERFACE IMPORTED GLOBAL)
     target_include_directories(LBFGSpp::LBFGSpp INTERFACE "${LBFGSpp_SOURCE_DIR}/include")
 endif()
-
+endif()
 if("${USE_QCINT}")
     set(LIBCINT_REPOSITORY "sunqm/qcint")
 else()
@@ -135,7 +142,7 @@ endif ()
 
 # Add compiler flags to fix the implicit function declaration error
 set(LIBCINT_C_FLAGS "-Wno-implicit-function-declaration -Wno-deprecated-non-prototype -D_GNU_SOURCE")
-
+if (NOT NIX_BUILD)
 CPMAddPackage(
     NAME libcint
     GITHUB_REPOSITORY "${LIBCINT_REPOSITORY}"
@@ -152,7 +159,7 @@ CPMAddPackage(
         ${LIBCINT_BUILD_TYPE}
     VERSION "6.1.2"
 )
-
+endif()
 # Apply the flags to the target after it's created
 if(TARGET cint)
     target_compile_options(cint PRIVATE 
@@ -160,7 +167,7 @@ if(TARGET cint)
         -Wno-deprecated-non-prototype
     )
 endif()
-
+if (NOT NIX_BUILD)
 add_library(libcint::libcint INTERFACE IMPORTED GLOBAL) 
 target_link_libraries(libcint::libcint INTERFACE cint)
 target_include_directories(
@@ -169,7 +176,7 @@ target_include_directories(
     "${libcint_SOURCE_DIR}/src"
     "${libcint_BINARY_DIR}/include"
 )
-
+endif()
 if(NOT "${USE_SYSTEM_LIBXC}")
 CPMAddPackage(
     NAME Libxc
@@ -188,11 +195,10 @@ target_include_directories(
     "${Libxc_BINARY_DIR}/src"
     "${Libxc_BINARY_DIR}"
 )
-
 endif()
 
 
-if("${WITH_PYTHON_BINDINGS}")
+if("${WITH_PYTHON_BINDINGS}" AND NOT NIX_BUILD)
 CPMAddPackage(
     NAME nanobind
     GITHUB_REPOSITORY "wjakob/nanobind"
diff --git a/3rdparty/nix/dftd4.nix b/3rdparty/nix/dftd4.nix
new file mode 100644
index 000000000..4944c11ef
--- /dev/null
+++ b/3rdparty/nix/dftd4.nix
@@ -0,0 +1,89 @@
+{
+  stdenv,
+  lib,
+  fetchFromGitHub,
+  buildType ? "cmake",
+  pkgs,
+  src,
+  version,
+}:
+
+assert !pkgs.blas.isILP64 && !pkgs.lapack.isILP64;
+assert (
+  builtins.elem buildType [
+    "meson"
+    "cmake"
+  ]
+);
+
+stdenv.mkDerivation {
+  pname = "dftd4";
+  inherit version;
+  inherit src;
+
+  nativeBuildInputs =
+    with pkgs;
+    [
+      gfortran
+      pkg-config
+      python3
+    ]
+    ++ lib.optionals (buildType == "meson") [
+      meson
+      ninja
+    ]
+    ++ lib.optional (buildType == "cmake") cmake;
+
+  buildInputs = with pkgs; [
+    blas
+    lapack
+    eigen
+  ];
+
+  propagatedBuildInputs = with pkgs; [
+    mctc-lib
+    mstore
+    multicharge
+  ];
+
+  cmakeFlags = [
+    (lib.strings.cmakeBool "BUILD_SHARED_LIBS" (!stdenv.hostPlatform.isStatic))
+    "-DDFTD4_USE_EIGEN=ON"
+    "-DBUILD_SHARED_LIBS=OFF"
+  ];
+
+  doCheck = true;
+
+  postPatch = ''
+    patchShebangs --build \
+      config/install-mod.py \
+      app/tester.py
+  '';
+
+  preCheck = ''
+    export OMP_NUM_THREADS=2
+  '';
+  postInstall = ''
+    TARGET_DIR="$out/lib/cmake/dftd4"
+        mkdir -p "$TARGET_DIR"
+
+        cat > "$TARGET_DIR/dftd4Config.cmake" <<EOF
+    include("\''${CMAKE_CURRENT_LIST_DIR}/dftd4Targets.cmake")
+
+    set_target_properties(dftd4::dftd4 PROPERTIES
+      INTERFACE_INCLUDE_DIRECTORIES "\''${CMAKE_CURRENT_LIST_DIR}/../../../include/dftd4"
+    )
+    EOF
+  '';
+  meta = {
+    description = "Generally Applicable Atomic-Charge Dependent London Dispersion Correction";
+    mainProgram = "dftd4";
+    license = with lib.licenses; [
+      lgpl3Plus
+      gpl3Plus
+    ];
+    homepage = "https://github.com/grimme-lab/dftd4";
+    platforms = lib.platforms.linux;
+    maintainers = [ lib.maintainers.sheepforce ];
+  };
+}
diff --git a/3rdparty/nix/gemmi.nix b/3rdparty/nix/gemmi.nix
new file mode 100644
index 000000000..b11fb2342
--- /dev/null
+++ b/3rdparty/nix/gemmi.nix
@@ -0,0 +1,29 @@
+{ pkgs, stdenv, ... }:
+stdenv.mkDerivation rec {
+  pname = "gemmi";
+  version = "0.6.5";
+  src = pkgs.fetchFromGitHub {
+    owner = "project-gemmi";
+    repo = "gemmi";
+    tag = "v${version}";
+    hash = "sha256-JJ6YBsdL3J+d0ihuJ2Nowp40c7FkDdfTqBhDrxWgSFw=";
+  };
+  dontBuild = true;
+  dontConfigure = true;
+
+  installPhase = ''
+      mkdir -p $out/include
+      cp -r include/* $out/include/
+      TARGET_DIR="$out/lib/cmake/gemmi"
+      mkdir -p "$TARGET_DIR"
+      cat > "$TARGET_DIR/gemmiConfig.cmake" <<EOF
+      if(NOT TARGET gemmi::gemmi)
+        add_library(gemmi::gemmi INTERFACE IMPORTED)
+      endif()
+
+      set_target_properties(gemmi::gemmi PROPERTIES
+        INTERFACE_INCLUDE_DIRECTORIES "$out/include"
+      )
+    EOF
+  '';
+}
diff --git a/3rdparty/nix/lbfgspp.nix b/3rdparty/nix/lbfgspp.nix
new file mode 100644
index 000000000..34f51f4ee
--- /dev/null
+++ b/3rdparty/nix/lbfgspp.nix
@@ -0,0 +1,29 @@
+{
+  lib,
+  stdenv,
+  cmake,
+  eigen,
+  version,
+  src,
+}:
+
+stdenv.mkDerivation {
+  pname = "lbfgspp";
+  inherit src;
+  inherit version;
+  nativeBuildInputs = [ cmake ];
+
+  propagatedBuildInputs = [ eigen ];
+
+  cmakeFlags = [
+    "-DCMAKE_INSTALL_INCLUDEDIR=include"
+  ];
+
+  meta = with lib; {
+    description = "A header-only C++ library for L-BFGS and L-BFGS-B algorithms";
+    homepage = "https://github.com/yixuan/LBFGSpp";
+    license = licenses.mit;
+    platforms = platforms.all;
+    maintainers = [ ];
+  };
+}
diff --git a/3rdparty/nix/libcint.nix b/3rdparty/nix/libcint.nix
new file mode 100644
index 000000000..7a6993f03
--- /dev/null
+++ b/3rdparty/nix/libcint.nix
@@ -0,0 +1,66 @@
+{
+  stdenv,
+  lib,
+  fetchFromGitHub,
+  cmake,
+  blas,
+  python3,
+  src,
+  version,
+}:
+
+stdenv.mkDerivation rec {
+  pname = "libcint";
+  inherit version;
+  inherit src;
+
+  postPatch = ''
+    sed -i 's/libcint.so/libcint${stdenv.hostPlatform.extensions.sharedLibrary}/g' testsuite/*.py
+    mkdir -p $out/lib/cmake/libcint
+    cat > $out/lib/cmake/libcint/libcintConfig.cmake <<EOF
+      set(Libcint_FOUND TRUE)
+      # Use placeholder "out" to refer to this package's installation path
+      set(LIBCINT_INCLUDE_DIRS "${placeholder "out"}/include")
+      set(LIBCINT_LIBRARIES "${placeholder "out"}/lib/libcint.a")
+      
+      if(NOT TARGET libcint::libcint)
+        add_library(libcint::libcint UNKNOWN IMPORTED)
+        set_target_properties(libcint::libcint PROPERTIES
+          IMPORTED_LOCATION "\''${LIBCINT_LIBRARIES}"
+          INTERFACE_INCLUDE_DIRECTORIES "\''${LIBCINT_INCLUDE_DIRS}"
+        )
+      endif()
+  '';
+  nativeBuildInputs = [ cmake ];
+  buildInputs = [ blas ];
+  cmakeFlags = [
+    "-DCMAKE_INSTALL_PREFIX=" # ends up double-adding /nix/store/... prefix, this avoids issue
+    "-DWITH_FORTRAN=OFF"
+    "-DWITH_CINT2_INTERFACE=OFF"
+    "-DENABLE_STATIC=ON"
+    "-DBUILD_SHARED_LIBS=OFF"
+    "-DPYPZPX=ON"
+    "-DBUILD_MARCH_NATIVE=ON"
+    "-DWITH_RANGE_COULOMB=ON"
+  ];
+  env.NIX_CFLAGS_COMPILE = "-Wno-implicit-function-declaration -Wno-deprecated-non-prototype -D_GNU_SOURCE";
+  strictDeps = true;
+
+  doCheck = true;
+  nativeCheckInputs = [ python3.pkgs.numpy ];
+
+  meta = {
+    description = "General GTO integrals for quantum chemistry";
+    longDescription = ''
+      libcint is an open source library for analytical Gaussian integrals.
+      It provides C/Fortran API to evaluate one-electron / two-electron
+      integrals for Cartesian / real-spheric / spinor Gaussian type functions.
+    '';
+    homepage = "http://wiki.sunqm.net/libcint";
+    downloadPage = "https://github.com/sunqm/libcint";
+    changelog = "https://github.com/sunqm/libcint/blob/master/ChangeLog";
+    license = lib.licenses.bsd2;
+    maintainers = [ ];
+    platforms = lib.platforms.unix;
+  };
+}
diff --git a/3rdparty/nix/scnlib.nix b/3rdparty/nix/scnlib.nix
new file mode 100644
index 000000000..778447108
--- /dev/null
+++ b/3rdparty/nix/scnlib.nix
@@ -0,0 +1,53 @@
+{
+  lib,
+  stdenv,
+  fetchFromGitHub,
+  cmake,
+  fast-float,
+  enableShared ? !stdenv.hostPlatform.isStatic,
+}:
+# Coppied from https://github.com/nix-community/nur-combined/tree/main/repos/foolnotion
+stdenv.mkDerivation rec {
+  pname = "scnlib";
+  version = "4.0.1";
+
+  src = fetchFromGitHub {
+    owner = "eliaskosunen";
+    repo = "scnlib";
+    rev = "v${version}";
+    sha256 = "sha256-qEZAWhtvhKMkh7fk1yD17ErWGCpztEs0seV4AkBOy1I=";
+  };
+
+  nativeBuildInputs = [ cmake ];
+  buildInputs = [ fast-float ];
+  postPatch = ''
+    substituteInPlace src/scn/impl.cpp \
+      --replace "fast_float::scientific" "fast_float::chars_format::scientific" \
+      --replace "fast_float::fixed" "fast_float::chars_format::fixed" \
+      --replace "fast_float::general" "fast_float::chars_format::general" \
+      --replace "fast_float::hex" "fast_float::chars_format::hex"
+  '';
+
+  cmakeFlags = [
+    "-DSCN_TESTS=OFF"
+    "-DSCN_EXAMPLES=OFF"
+    "-DSCN_BENCHMARKS=OFF"
+    "-DSCN_BENCHMARKS_BUILDTIME=OFF"
+    "-DSCN_BENCHMARKS_BINARYSIZE=OFF"
+    "-DSCN_USE_EXTERNAL_BENCHMARK=ON"
+    "-DSCN_USE_EXTERNAL_FAST_FLOAT=ON"
+    "-DENABLE_FULL=OFF"
+    "-DSCN_INSTALL=ON"
+    "-DBUILD_SHARED_LIBS=${if enableShared then "ON" else "OFF"}"
+  ];
+  # postInstall = ''
+  #   ln -s $out/lib/cmake/scn/scn-config.cmake $out/lib/cmake/scn/scnlibConfig.cmake
+  # '';
+  meta = with lib; {
+    description = "Modern C++ library for replacing scanf and std::istream";
+    homepage = "https://scnlib.readthedocs.io/";
+    license = licenses.asl20;
+    platforms = platforms.all;
+    #maintainers = with maintainers; [ foolnotion ];
+  };
+}
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a2b5b7ba4..739d604bf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -130,6 +130,23 @@ endif()
 
 include("${CMAKE_CURRENT_SOURCE_DIR}/cmake/CPM.cmake")
 # don't use install commands from third party
+if (NIX_BUILD)
+find_package(fmt REQUIRED)
+find_package(spdlog REQUIRED)
+add_library(spdlog::spdlog ALIAS spdlog::spdlog_header_only)
+find_package(TBB REQUIRED)
+find_package(scn REQUIRED)
+find_package(unordered_dense REQUIRED)
+find_package(CLI11 REQUIRED)
+find_package(nlohmann_json REQUIRED)
+find_package(gemmi REQUIRED)
+find_package(dftd4 REQUIRED)
+find_package(lbfgspp REQUIRED)
+add_library(LBFGSpp::LBFGSpp ALIAS lbfgspp)
+find_package(libcint REQUIRED)
+find_package(Libxc REQUIRED)
+find_package(nanobind REQUIRED)
+endif ()
 add_subdirectory(3rdparty EXCLUDE_FROM_ALL)
 add_subdirectory(include)
 add_subdirectory(src)
diff --git a/cmake/CPM.cmake b/cmake/CPM.cmake
index 47e2e872a..c272e953f 100644
--- a/cmake/CPM.cmake
+++ b/cmake/CPM.cmake
@@ -4,21 +4,22 @@
 
 set(CPM_DOWNLOAD_VERSION 0.40.5)
 set(CPM_HASH_SUM "c46b876ae3b9f994b4f05a4c15553e0485636862064f1fcc9d8b4f832086bc5d")
+if (NOT NIX_BUILD)
+  if(CPM_SOURCE_CACHE)
+    set(CPM_DOWNLOAD_LOCATION "${CPM_SOURCE_CACHE}/cpm/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
+  elseif(DEFINED ENV{CPM_SOURCE_CACHE})
+    set(CPM_DOWNLOAD_LOCATION "$ENV{CPM_SOURCE_CACHE}/cpm/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
+  else()
+    set(CPM_DOWNLOAD_LOCATION "${CMAKE_BINARY_DIR}/cmake/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
+  endif()
+  # Expand relative path. This is important if the provided path contains a tilde (~)
+  get_filename_component(CPM_DOWNLOAD_LOCATION ${CPM_DOWNLOAD_LOCATION} ABSOLUTE)
 
-if(CPM_SOURCE_CACHE)
-  set(CPM_DOWNLOAD_LOCATION "${CPM_SOURCE_CACHE}/cpm/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
-elseif(DEFINED ENV{CPM_SOURCE_CACHE})
-  set(CPM_DOWNLOAD_LOCATION "$ENV{CPM_SOURCE_CACHE}/cpm/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
-else()
-  set(CPM_DOWNLOAD_LOCATION "${CMAKE_BINARY_DIR}/cmake/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
-endif()
+  file(DOWNLOAD
+    https://github.com/cpm-cmake/CPM.cmake/releases/download/v${CPM_DOWNLOAD_VERSION}/CPM.cmake
+    ${CPM_DOWNLOAD_LOCATION} EXPECTED_HASH SHA256=${CPM_HASH_SUM}
+  )
+endif ()
 
-# Expand relative path. This is important if the provided path contains a tilde (~)
-get_filename_component(CPM_DOWNLOAD_LOCATION ${CPM_DOWNLOAD_LOCATION} ABSOLUTE)
-
-file(DOWNLOAD
-     https://github.com/cpm-cmake/CPM.cmake/releases/download/v${CPM_DOWNLOAD_VERSION}/CPM.cmake
-     ${CPM_DOWNLOAD_LOCATION} EXPECTED_HASH SHA256=${CPM_HASH_SUM}
-)
 
 include(${CPM_DOWNLOAD_LOCATION})
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 000000000..efad62c9f
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,116 @@
+{
+  "nodes": {
+    "dftd4-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1741937608,
+        "narHash": "sha256-aBWw9DGt0s5nGvmHQZzuZDPTWRGCsaKCrp4NylHOzqw=",
+        "owner": "peterspackman",
+        "repo": "cpp-d4",
+        "rev": "792e97c45699faf96813dd1df654fea79ab4fdcc",
+        "type": "github"
+      },
+      "original": {
+        "owner": "peterspackman",
+        "ref": "main",
+        "repo": "cpp-d4",
+        "type": "github"
+      }
+    },
+    "fast-float-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1725816977,
+        "narHash": "sha256-MEJMPQZZZhOFiKlPAKIi0zVzaJBvjAlbSyg3wLOQ1fg=",
+        "owner": "fastfloat",
+        "repo": "fast_float",
+        "rev": "00c8c7b0d5c722d2212568d915a39ea73b08b973",
+        "type": "github"
+      },
+      "original": {
+        "owner": "fastfloat",
+        "ref": "v6.1.6",
+        "repo": "fast_float",
+        "type": "github"
+      }
+    },
+    "gemmi-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1708169757,
+        "narHash": "sha256-JJ6YBsdL3J+d0ihuJ2Nowp40c7FkDdfTqBhDrxWgSFw=",
+        "owner": "project-gemmi",
+        "repo": "gemmi",
+        "rev": "e471b13704c3bb0a6fc53c70b838df0dfa2088e1",
+        "type": "github"
+      },
+      "original": {
+        "owner": "project-gemmi",
+        "ref": "v0.6.5",
+        "repo": "gemmi",
+        "type": "github"
+      }
+    },
+    "lbfgspp-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1745147553,
+        "narHash": "sha256-PUzZ2jUVgHq1LJDWIWW93KnV7vBBEdZlspOrE5TcYBc=",
+        "owner": "yixuan",
+        "repo": "LBFGSpp",
+        "rev": "c524a407fb85b74807f53de5a3ca2ddbcc164e54",
+        "type": "github"
+      },
+      "original": {
+        "owner": "yixuan",
+        "ref": "v0.4.0",
+        "repo": "LBFGSpp",
+        "type": "github"
+      }
+    },
+    "libcint-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1752539348,
+        "narHash": "sha256-JWk1B+Fz5nHxnGI5WlSynNqvkqIRvkbba8Nx3I5Tziw=",
+        "owner": "peterspackman",
+        "repo": "libcint",
+        "rev": "644c68c695ac4f20fb5838391a01931e9484650b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "peterspackman",
+        "repo": "libcint",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1769789167,
+        "narHash": "sha256-kKB3bqYJU5nzYeIROI82Ef9VtTbu4uA3YydSk/Bioa8=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "62c8382960464ceb98ea593cb8321a2cf8f9e3e5",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "dftd4-src": "dftd4-src",
+        "fast-float-src": "fast-float-src",
+        "gemmi-src": "gemmi-src",
+        "lbfgspp-src": "lbfgspp-src",
+        "libcint-src": "libcint-src",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 000000000..7dadd2c29
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,185 @@
+{
+  description = "Open Computational Chemestry";
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    fast-float-src = {
+      url = "github:fastfloat/fast_float?ref=v6.1.6";
+      flake = false;
+    };
+    dftd4-src = {
+      url = "github:peterspackman/cpp-d4?ref=main";
+      flake = false;
+    };
+    lbfgspp-src = {
+      url = "github:yixuan/LBFGSpp?ref=v0.4.0";
+      flake = false;
+    };
+    libcint-src = {
+      url = "github:peterspackman/libcint";
+      flake = false;
+    };
+    gemmi-src = {
+      url = "github:project-gemmi/gemmi?ref=v0.6.5";
+      flake = false;
+    };
+  };
+  outputs =
+    {
+      self,
+      nixpkgs,
+      fast-float-src,
+      dftd4-src,
+      lbfgspp-src,
+      libcint-src,
+      gemmi-src,
+    }:
+    let
+      system = "x86_64-linux";
+      pkgs = nixpkgs.legacyPackages.${system};
+      fast-float-6_1_6 = pkgs.fast-float.overrideAttrs {
+        src = fast-float-src;
+        version = "6.1.6";
+      };
+      scnlib = pkgs.callPackage ./3rdparty/nix/scnlib.nix {
+        fast-float = fast-float-6_1_6;
+      };
+      dftd4 = pkgs.callPackage ./3rdparty/nix/dftd4.nix {
+        src = dftd4-src;
+        version = "main";
+      };
+      lbfgspp = pkgs.callPackage ./3rdparty/nix/lbfgspp.nix {
+        src = lbfgspp-src;
+        version = "0.4.0";
+      };
+      libcint = pkgs.callPackage ./3rdparty/nix/libcint.nix {
+        version = "6.1.2";
+        src = libcint-src;
+      };
+      gemmi = pkgs.callPackage ./3rdparty/nix/gemmi.nix {
+        version = "0.6.5";
+        src = gemmi-src;
+      };
+      python = pkgs.python314.withPackages (ps: [ ps.nanobind ]);
+      CMAKE_PREFIX_PATH = "${python}/${python.sitePackages}";
+    in
+    {
+      # 1. The Build Artifact (nix build)
+      packages.${system} = {
+        python = python;
+        default = pkgs.stdenv.mkDerivation {
+          name = "occ";
+          src = ./.;
+          postPatch = ''
+            rm cmake/FindLibxc.cmake
+          '';
+          buildInputs = with pkgs; [
+            cmake
+            python
+            cpm-cmake
+            pkg-config
+            spdlog
+            onetbb
+            tomlplusplus
+            unordered_dense
+            fmt
+            nlohmann_json
+            eigen_3_4_0
+            libxc.dev
+            cli11
+            gemmi
+            ccache
+            gfortran.cc.lib
+            zlib
+            scnlib
+            dftd4
+            libcint
+            lbfgspp
+            fast-float-6_1_6
+          ];
+          nativeBuildInputs = [
+            pkgs.cmake
+            pkgs.ninja
+            pkgs.pkg-config
+            pkgs.ccache
+          ];
+          env = {
+            CCACHE_DIR = "/var/cache/ccache";
+            CCACHE_BASEDIR = "$NIX_BUILD_TOP";
+            CCACHE_SLOPPINESS = "locale,time_macros";
+            CMAKE_PREFIX_PATH = "${CMAKE_PREFIX_PATH}";
+          };
+          cmakeFlags = [
+            "-GNinja"
+            "-DCPM_DOWNLOAD_LOCATION=${pkgs.cpm-cmake}/share/cpm/CPM.cmake"
+            "-DUSE_SYSTEM_EIGEN=ON"
+            "-DUSE_SYSTEM_LIBXC=ON"
+            "-DCPM_USE_LOCAL_PACKAGES=ON"
+            "-DCMAKE_C_COMPILER_LAUNCHER=${pkgs.ccache}/bin/ccache"
+            "-DCMAKE_CXX_COMPILER_LAUNCHER=${pkgs.ccache}/bin/ccache"
+            "-DNIX_BUILD=ON"
+            "-DWITH_PYTHON_BINDINGS=ON"
+          ];
+          NIX_LDFLAGS = "-lquadmath";
+        };
+        gemmi = gemmi;
+        libxc = pkgs.libxc.dev;
+      };
+
+      # 2. The Development Environment (nix develop)
+      devShells.${system}.default = pkgs.mkShell {
+        inputsFrom = [ self.packages.${system}.default ];
+
+        # Extra development-only tools
+        nativeBuildInputs = with pkgs; [
+          llvm
+          gcc
+          gdb
+          ninja
+          clang-tools
+          lld
+        ];
+
+        shellHook =
+          let
+            # List all dependencies that CMake needs to find
+            deps = [
+              pkgs.spdlog
+              pkgs.onetbb
+              pkgs.tomlplusplus
+              pkgs.unordered_dense
+              pkgs.fmt
+              pkgs.nlohmann_json
+              pkgs.eigen_3_4_0
+              pkgs.libxc
+              pkgs.cli11
+              gemmi
+              scnlib
+              dftd4
+              libcint
+              lbfgspp
+              fast-float-6_1_6
+            ];
+            runtimeLibs = with pkgs; [
+              stdenv.cc.cc.lib
+              zlib
+              glib
+            ];
+            buildInputs = with pkgs; [
+              uv
+            ];
+          in
+          ''
+            # Construct CMAKE_PREFIX_PATH by joining the store paths with semicolons
+            export CMAKE_PREFIX_PATH="${
+              pkgs.lib.makeSearchPathOutput "dev" "" deps
+            }:${pkgs.lib.makeBinPath deps}"
+
+            # Also export PKG_CONFIG_PATH just in case some libs don't have CMake configs
+            export PKG_CONFIG_PATH="${pkgs.lib.makeSearchPathOutput "dev" "lib/pkgconfig" deps}:./cmake"
+
+            export LD_LIBRARY_PATH="${pkgs.lib.makeLibraryPath runtimeLibs}"
+          '';
+
+      };
+    };
+}
diff --git a/pyproject.toml b/pyproject.toml
index 0376c79e3..7b32f1f5c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -52,4 +52,11 @@ MACOSX_DEPLOYMENT_TARGET = "10.15"
 
 # Pyodide doesn't support C++ exceptions - disable them and abort on throw
 [tool.cibuildwheel.pyodide.environment]
-CMAKE_ARGS = "-DCMAKE_CXX_FLAGS=-fno-exceptions"
+CMAKE_ARGS = "-DCMAKE_CXX_FLAGS=-fno-exceptions -DWITH_PYTHON_BINDINGS=ON"
+
+[tool.uv.workspace]
+members = [
+    "tests-py",
+    ".",
+    ".",
+]
diff --git a/src/occpy.cpp b/src/occpy.cpp
index 9b1a2a262..274bff1ce 100644
--- a/src/occpy.cpp
+++ b/src/occpy.cpp
@@ -23,7 +23,7 @@
 
 namespace nb = nanobind;
 
-NB_MODULE(_occpy, m) {
+__attribute__ ((visibility ("default"))) NB_MODULE(_occpy, m) {
   // Register core submodule
   auto core = register_core_bindings(m);
   auto cg = register_cg_bindings(m);
diff --git a/src/python/crystal_bindings.cpp b/src/python/crystal_bindings.cpp
index f36d89653..b891ca187 100644
--- a/src/python/crystal_bindings.cpp
+++ b/src/python/crystal_bindings.cpp
@@ -121,6 +121,7 @@ nb::module_ register_crystal_bindings(nb::module_ &m) {
                     const UnitCell &>())
       .def("symmetry_unique_molecules", &Crystal::symmetry_unique_molecules)
       .def("symmetry_unique_dimers", &Crystal::symmetry_unique_dimers)
+      .def("symmetry_operations", &Crystal::symmetry_operations)
       .def("unit_cell", &Crystal::unit_cell)
       .def("unit_cell_molecules", &Crystal::unit_cell_molecules)
       .def("unit_cell_atoms", &Crystal::unit_cell_atoms)