GEOMETRIC AND ELECTRONIC-STRUCTURE OF GROUND AND EXCITED-STATES OF GROUP VA DIATOMICS - A THEORETICAL LCGTO-MP-LSD STUDY

LCGTO-MP-LSD calculation was performed for the ground and several low- lying excited states of homo- (N2, P2, As2, and Sb2) and hetero-nuclea r (PN, AsN, AsP, AsSb, SbN, and SbP) group VA diatomics. For all the s ystems the ground state is found to be (1)SIGMA+. For N2 and P2, the ( 1)SIGMA(g)+ ground state is followed by the (3)SIGMA(u)+, (3)PI(g), (3 )DELTA(u), (1)PI(g), and (1)DELTA(u) low-lying exited states while for As2 the order is found to be (3)SIGMA(u)+, (3)DELTA(u), (3)PI(g), (1) DELTA(u), (1)PI(g). Finally for Sb2 the relative stability of excited states is (3)SIGMA(u)+, (3)DELTA(u), (1)DELTA(u), (3)PI(g), (1)PI(g). For the hetero-nuclear diatomics the (1)SIGMA+ ground state is, in the case of PN, AsN, AsP, SbN, and SbP, followed by the (3)SIGMA+, (3)DEL TA, (3)PI, (1)PI and (1)DELTA low-lying excited states while for the A sSb diatomic an inversion of stability of the two last singlets occurs . The calculated spectroscopic parameters (Re, omega-e, and De) are in good agreement with all the available experimental results while, the Te values are overestimated by about 0.5 eV. Mulliken population anal ysis shows that both homo- and hetero-nuclear group VA diatomics are e ssentially triple bonded systems.