Ab initio calculation of accurate dissociation energy, potential energy curve and dipole moment function for the A1∑ + state 7LiH molecule

The reasonable dissociation limit of the A¹∑⁺ state$^{7}$LiH molecule is obtained. The accurate dissociation energy and theequilibrium geometry of this state are calculated using asymmetry-adapted-cluster configuration-interaction method in complete active spacefor the first time. The whole potential energy curve and the dipole momentfunction for theA¹∑⁺ state are calculated over a wideinternuclear separation range from about 0.1 to 1.4,nm. The calculatedequilibrium geometry and dissociation energy of this potential energy curveare of R_{e}=0.2487,nm and D_{e}=1.064,eV, respectively. The unusual negativevalues of the anharmonicity constant and the vibration-rotational couplingconstant are of textit{omega }_{e}textit{chi}_{e}=--4.7158cm^{ - 1} and textit{alpha}_{e}=--0.08649cm^{ -1}, respectively. The vertical excitationenergy from the ground to theA¹∑⁺ state is calculated and the value is of 3.613,eV at0.15875nm (the equilibrium position of the ground state). The highlyanomalous shape of this potential energy curve, which is exceptionally flatover a wide radial range around the equilibrium position, is discussed indetail. The harmonic frequency value of 502.47cm¹ about this stateis approximately estimated. Careful comparison of the theoreticaldeterminations with those obtained by previous theories about theA¹∑⁺ state dissociation energy clearly shows that the presentcalculations are much closer to the experiments than previous theories, thusrepresents an improvement.

Ab initio calculation of accurate dissociation energy, potential energy curve and dipole moment function for the A1∑ + state 7LiH molecule

The reasonable dissociation limit of the A¹∑⁺ state$^{7}$LiH molecule is obtained. The accurate dissociation energy and theequilibrium geometry of this state are calculated using asymmetry-adapted-cluster configuration-interaction method in complete active spacefor the first time. The whole potential energy curve and the dipole momentfunction for theA¹∑⁺ state are calculated over a wideinternuclear separation range from about 0.1 to 1.4,nm. The calculatedequilibrium geometry and dissociation energy of this potential energy curveare of R_{e}=0.2487,nm and D_{e}=1.064,eV, respectively. The unusual negativevalues of the anharmonicity constant and the vibration-rotational couplingconstant are of textit{omega }_{e}textit{chi}_{e}=--4.7158cm^{ - 1} and textit{alpha}_{e}=--0.08649cm^{ -1}, respectively. The vertical excitationenergy from the ground to theA¹∑⁺ state is calculated and the value is of 3.613,eV at0.15875nm (the equilibrium position of the ground state). The highlyanomalous shape of this potential energy curve, which is exceptionally flatover a wide radial range around the equilibrium position, is discussed indetail. The harmonic frequency value of 502.47cm¹ about this stateis approximately estimated. Careful comparison of the theoreticaldeterminations with those obtained by previous theories about theA¹∑⁺ state dissociation energy clearly shows that the presentcalculations are much closer to the experiments than previous theories, thusrepresents an improvement.