Abstract
In this study, the three forms of B2N(−, 0, +)—radical, anion and cation—have been compared in terms of electric potential and atomic charges, ESP, rather than the well-known cut of the potential energy surface (PES). We have realized that the double minimum of the BNB radical is related to the lack of the correct permutational symmetry of the wave function and charge distribution. The symmetry breaking (SB) for B2N(0, +) exhibits energy barrier in the region of (5–150) cm−1. The SB barrier goes through a dynamic change with no centrosymmetric form which depends on the wave function or charge distribution. In spite of exited state, the excited configuration contributes to the ground state ( for forming radicals. The SB did not occur for the anion form (B2N(−)) in any electrostatic potential and charges distribution. Finally, we have modified the Columbic term of the Schrödinger equation to define the parameters “αα' and ββ'” in order to investigate the SBs subject.
Highlights
Linear triatomic structures, those of the X-Y-X type are one of the simplest molecular systems with “high” symmetry in which symmetry breaking (SB) may occur
We have shown that the SB problem is not a real phenomenon; it is a hidden function depending on various variables such as charge distribution, bond length, Isotropic Fermi contact coupling (IFCC), primitive Gaussians, trial wave-function properties, frozen core electrons and most importantly, non-Born–Oppenheimer approximation approach
While the nuclear repulsion energy of B2Np,0,`q in Born–Oppenheimer approximation mostly depends on the variables such as B-N bond length, using large and larger basis sets and more and more electron correlation are doomed to result in wrong limit for the energy level of SB barriers or SB estimation
Summary
Those of the X-Y-X type are one of the simplest molecular systems with “high” symmetry in which symmetry breaking (SB) may occur. In 2009, a series of multi-reference approaches based on the SA-CASSCF wave function, i.e., CASPT2, MRCI, and MRAQCC, have been employed by Boggs and coworkers to investigate the SB in the ground state Xr2Σpuq of the triatomic B2N(0) radical [20] Their results show that B2N in its ground state has a linear non-centrosymmetric structure with two equivalent global minima of the adiabatic potential energy surface, including two oppositely directed dipole moments, respectively. They accepted that the PJT effect involving vibronic interaction with the first excited state Ar2Σpgq via the asymmetric stretching vibrations is the major reason for the double-minimum. This work has focused on a spontaneous symmetry breaking (SSB) [25,26,27] for B2Np,0,`q systems in view of ESP
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