" /> " /> " /> sodalite (295-1200 K) based on single-crystal neutron diffraction and an anharmonic thermal vibration model for Na+, Cl− and O indicate (i) the thermal expansion from an untwisting of the aluminosilicate framework due to increasing translational motions of Na+ coupled with librations of SiO4/AlO4 tetrahedra and (ii) Na+-Cl− diffusion along <111> channels. sodalite (295-1200 K) based on single-crystal neutron diffraction and an anharmonic thermal vibration model for Na+, Cl− and O indicate (i) the thermal expansion from an untwisting of the aluminosilicate framework due to increasing translational motions of Na+ coupled with librations of SiO4/AlO4 tetrahedra and (ii) Na+-Cl− diffusion along <111> channels. sodalite (295-1200 K) based on single-crystal neutron diffraction and an anharmonic thermal vibration model for Na+, Cl− and O indicate (i) the thermal expansion from an untwisting of the aluminosilicate framework due to increasing translational motions of Na+ coupled with librations of SiO4/AlO4 tetrahedra and (ii) Na+-Cl− diffusion along <111> channels.