zerodipole

Zerodipole is a term used in physics and chemistry to describe a system, configuration, or model that has a vanishing electric dipole moment. The electric dipole moment is a vector that characterizes the separation of positive and negative charges in a distribution; when it sums to zero, there is no net first-order charge separation.

Zero dipole moments arise from symmetry in the charge distribution. For example, many highly symmetric molecules such as methane (CH4), carbon dioxide (CO2), and homonuclear diatomic molecules like oxygen (O2) exhibit zero permanent dipole moment. The absence of a dipole does not imply the absence of higher-order multipoles; such molecules can still possess nonzero quadrupole or octupole moments, which influence interactions at longer ranges and affect certain spectroscopic features.

In practice, the concept appears in different contexts. In spectroscopy, a zero dipole moment can render some vibrational transitions IR-inactive because they do not involve a change in dipole. In computational and materials studies, zerodipole considerations or boundary conditions are used to reduce artificial electric fields at the edges of finite simulations, particularly for systems with no intrinsic dipole.

The term zerodipole is not tied to a single canonical definition and is often used informally to describe cases with vanishing dipole moments or related modeling considerations. It relates to the broader framework of multipole expansion and is commonly contrasted with systems that retain a nonzero dipole moment.