On the structures, stabilities, and potential energy surfaces of planar BnN (n = 1-6) clusters

► The lowest-energy structures (1a-6a) of planar BnN (n = 1-6) are obtained. ► BnN (n = 1-6) exhibit linear to polycyclic structure transition. ► BnN with n = 2 and 5 have relatively higher stability. ► The growth pattern and bonding nature of BnN (n = 1-6) are revealed. ► The thermodynamic and kinetic stability of BnN (n = 1-6) is examined.