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Ab initio calculation of accurate dissociation energy, potential energy curve and dipole moment function for the A1∑ + state 7LiH molecule
Shi De-Heng, Liu Yu-Fang, Sun Jin-Feng, Yang Xiang-Dong, Zhu Zun-Lue
2006, 15 (5):
1015-1021.
doi: 10.1088/1009-1963/15/5/025
Abstract
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PDF (283KB)
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The reasonable dissociation limit of the A1∑+ state
$^{7}$LiH molecule is obtained. The accurate dissociation energy and the
equilibrium geometry of this state are calculated using a
symmetry-adapted-cluster configuration-interaction method in complete active space
for the first time. The whole potential energy curve and the dipole moment
function for theA1∑+ state are calculated over a wide
internuclear separation range from about 0.1 to 1.4\,nm. The calculated
equilibrium geometry and dissociation energy of this potential energy curve
are of R_{\e}=0.2487\,nm and D_{\e}=1.064\,eV, respectively. The unusual negative
values of the anharmonicity constant and the vibration-rotational coupling
constant are of \textit{\omega }_{\e}\textit{\chi
}_{\e}=--4.7158cm^{ - 1} and \textit{\alpha
}_{\e}=--0.08649cm^{ -1}, respectively. The vertical excitation
energy from the ground to the
A1∑+ state is calculated and the value is of 3.613\,eV at
0.15875nm (the equilibrium position of the ground state). The highly
anomalous shape of this potential energy curve, which is exceptionally flat
over a wide radial range around the equilibrium position, is discussed in
detail. The harmonic frequency value of 502.47cm1 about this state
is approximately estimated. Careful comparison of the theoretical
determinations with those obtained by previous theories about the
A1∑+ state dissociation energy clearly shows that the present
calculations are much closer to the experiments than previous theories, thus
represents an improvement.
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