[en] The electron capture nuclear decay rate is proportional to the electron density at the nucleus and affected by the chemical environment, particularly in the case of electron capturing ⁷Be. In the case of higher Z elements, such effect is expected to be negligible as the valence electrons contribute very insignificant percentage of electron density at the nucleus. The change of electron capture nuclear decay rate of ⁷Be in different chemical environments has been observed experimentally and density functional calculations calculating the change of electron density at the nucleus generally give a reasonable explanation of the effect