MRCI Potential Curves And Analytical Potential Energy Functions Of The Group ⅡB Metal Dimers

The group IIB metal dimers such as HgZn, ZnCd and HgCd are of great importance in laser techniques, and have been suggested as high-efficiency laser systems. In the present paper, the potential energy curves (PECs) of the ground electronic state (1Σ+) and three low-lying excited electronic states (3Σ,1Π,3Π) of the three systems have been calculated using high-level ab initio method (the multireference configuration interaction method) by employing different basis sets. The obtained PECs of each states and systems have been fitted to the analytical potential energy functions (APEFs) using the Murrel-Sorbie (MS) potential function through nonlinear curve fit method. By calculating the quardratic, cubic and quartic force constants of the APEFs, we can determine the spectroscopic constants of each electronic state, including the harmonic vibrational frequencyωe, the inharmonic vibrational factorωeχe, the rigid-rotational factor Be, the nonrigid-rotational factor ae and the rotational constant Drot. Based on the ab initio PECs, the vibrational energy levels of each state have been predicted by solving the Schr?dinger equation of nuclear motion.For the HgZn system, we calculated the PECs of the ground state (1Σ+) using four groups of basis sets formed by full electronic basis sets and effective core potentials (ECPs). They are Ahlrichs-VTZ)Zn/(ECP60MWB)Hg , (ECP10MDF)Zn/(ECP60MWB)Hg, (Ahlrichs-pVDZ)Zn/(ECP60MWB)Hg and (ECP10MDF)Zn/(ECP78MWB)Hg. Totally, 6 curves of this state are calculated, of which 4 curves are obtained by CISD method, and the left two are obtained by MRCI treat. Based on the calculations of the ground state, we calculated the PECs of the excited electronic states (1Π,3Π) of the HgZn dimer using the effective core potential basis sets (ECP28MWB)Zn/(ECP60MWB)Hg. Based on the obtained PECs, we calculated the spectroscopic constants and predicted the vibrational levels, and the results are compared to theoretical as well as experimental reports available at present.The basis sets LANL2DZ have been used to calculate the PECs of the ground state (1Σ+) as well as the low-lying excited states (3Σ,1Π,3Π) of the ZnCd molecule. In order to compare the three excited states conveniently, we calculated them at the same time, which enables the fact that in the calculation process, the occupational orbital wave functions which is used in the CI calculation are the same. As there is no experimental works on the ZnCd system, we only compared our results with the present theoretical reports. As for the HgCd system, it is difficult for us to find the same basis sets for both the ground state and the excited states. As a result, we employed ten groups of basis sets to calculate the PECs of HgCd, they are ECP60MWB)Hg/(LANL2DZ)Cd ,(ECP78MHF)Hg/(ECP28MWB)Cd , (ECP78MWB)Hg/(ECP28MHF)Cd ,(ECP60MDF)Hg/ECP1 , (ECP1)Hg/(LANL2DZ)Cd , (ECP78MWB)Hg/(ECP1)Cd ,(ECP78MHF)Hg/(ECP1)Cd , (ECP78MWB)Hg/(LANL2DZ)Cd , (ECP1)Hg/(ECP1)Cd ,(ECP60MDF)Hg/(LANL2DZ)Cd. Totally, sixteen PECs have been obtained for the four states, and each PEC has been fitted to the APEF using the MS potential function. Furthermore, the corresponding spectroscopic constants and vibrational energy levels have also been calculated, which are compared to the present theoretical as well as experimental researches.