  $\text{N}_{2}\text{V}$ defect in diamond is characterized by means of
\emph{ab initio} methods relying on density functional theory calculated
parameters of a Hubbard model Hamiltonian. It is shown that this approach
appropriately describes the energy levels of correlated excited states induced
by this defect. By determining its critical magneto-optical parameters, we
propose to realize a long-living quantum memory by $\text{N}_{2}\text{V}$
defect in diamond.
