chemistry journal of moldova

N.Gorinchoy et al./Chem.J.Mold. 2008, 3 (1), 105-111Table 1Optimized geometries (Å), total energies (hartree), relative energies (eV) and electronic configurations of the groundand low-lying excited states for symmetry nuclear configurationsSymmetry Geometry State Total energy RelativeenergyElectronic configurationD hR O-O=1.30R O-H=0.94C 2hR O-O=1.39R O-H=0.94HOO=101.6°C 2vR O-O=1.39R O-H=0.94HOO=107.3°aC 2R O-O=1.39R O-H=0.94HOO=103.2° dihedral=110.2°+ g-150.6219 u-150.4905 g-150.3415A g-150.8533A u-150.5966A 1-150.8496A 2-150.5872a Experimental values of the angles: HOO=94.8 ° , HOOH= 111.5° [1].03.577.6306.9807.14[…( u) 4 ( g) 4 ( u) 0 ( g) 0 ][…( u) 4 ( g) 3 ( u) 1 ( g) 0 ][…( u) 4 ( g) 3 ( u) 0 ( g) 1 ][…(a g) 2 (b g) 2 (b u) 0 (a g) 0 ][…(a g) 2 (b g) 1 (b u) 1 (a g) 0 ][…(b 2) 2 (a 2) 2 (a 1) 0 (b 2) 0 ][…(b 2) 2 (a 2) 1 (a 1) 1 (b 2) 0 ]A -150. 8595 0 […(a) 2 (b) 2 (a) 0 (b) 0 ]The scheme of the electronic terms is shown in Fig. 2, where the dashed lines indicate the alteration of the statesunder the vibronically stabilized distortions. It is seen that in the high-symmetry linear (D h) nuclear configuration thesystem has a nondegenerate ground state 1 g+, and two low-lying two-fold degenerate 1 uand 1 gexcited electronic states.As was mentioned in the previous Section, only the vibronic constants of the type Fu g ( Hˆ( r,q) / q) u 0 uandF g g ( Hˆ( r,q) / q) g 0 g, and hence only the vibronic contribution to the curvature of the adiabaticvvpotential K and Ku are nonzero. If these values are large enough, the linear configuration is unstable withgrespect to uand gtypes nuclear displacements, and the system passes to more stable cis- (C 2v) or trans- (C 2h) nuclearconfigurations. In their turn due to the pseudo JT coupling of the ground 1 A g(C 2h) or 1 A 1(C 2v) and excited 1 A u(or 1 A 2)electronic states (i.e. non-zero Fa Ag( Hˆ( r,q) / qa) Au u 0 u and Fa A1 ( Hˆ( r,q) / q)2a20 A2vibronicconstants) these bent shapes become unstable with respect to the out-of-plane (a uor a 2type) displacements of thehydrogen atoms resulting in the equilibrium “skewed” anticline configuration of the C 2symmetry.Fig. 2. Electronic terms of the H 2O 2molecule in four symmetry configurations108