Theoretical Study Of The Dynamics And Potential Energy For Li₂K Molecular

In the last decade, ultracold molecules are currently a topic of much interest in theatomic and molecular physics investigations. KLi, which can be used in experiment inultracold temperature, has stimulated great interests in research. Investigations including theexperimental and theoretical efforts have been devoted to KLi molecule. But the researcheswere not very perfect and corresponding data obtained in previous theoretical studies wereincomplete. Be, as an element in the same period as that of Li, combines K into KBe moleculewhich is potent to become the candidates of ultracold experiment, but no investigation hasbeen found for KBe molecule to date. The alkali molecules containing boron atom, anelement in the same period as that of Li and Be, are species of chemical and biologicalimportance have caused a great deal of research interests. Several theoretical studies havebeen performed on BLi and BNa, but there are still a lot of disputes about their electronicstructure. No investigation has been found for BK molecule up to date. Therefore, weperformed high-quality ab initio calculations on the potential energy curves (PECs),ro-vibrational energy levels, spectroscopic parameters, dipole moment functions, transitiondipole moments and analytical potential energy functions (APEFs) for KLi, KBe and BAlk(Alk=Li, Na, K) molecules. The effects of inner-shell correlation electron are taken intoconsideration.The PECs have been calculated for the X1Σ+, A1Σ+,13Σ+,23Σ+states of KLi usingmultireference configuration interaction method and large all-electron basis setsdef2-AQZVPP-JKFI for K, aug-cc-pCV5Z for Li. The calculations take into account theeffect of inner-shell electrons with different active spaces. The rotational and vibrationalenergy levels are obtained by solving the Schr dinger equation of nuclear motion based onthe PECs. The spectroscopic parameters are determined from the ro-vibrational levels withDunham expansion and compared with the theoretical and experimental reports in theliterature. The PECs are fitted into APEFs using the Morse long-range (MLR) potentialfunction. The results show that the vibrational energy levels and the spectroscopic parametersfor the four states based on the active space including3s23p64s24p6of K and1s22s22p6of Liare in good agreement with the available data in the literature. It is found that the effect ofinner-shell electrons should be included in the calculation for KLi molecule, however, the active space containing additional3s23p6shells is enough to obtain satisfactory results for thefour states. The APEFs, which have been derived from MLR, can accurately reproduce theinteraction energy between K and Li.The PECs, ro-vibrational levels and spectroscopic parameters have been calculated for12Σ+,22Σ+,12Π and22Π states of KBe using the same method as KLi and large all-electronbasis sets def2-AQZVPP-JKFI for K, aug-cc-pCV5Z for Be. It is found that the effect ofinner-shell correlation electron plays obvious role on the molecular properties for the allconsidered states of KBe and the calculation based on the small-core approximation can giveaccurate results. The APEFs, which have been induced from the ab initio PECs, canaccurately reproduce the interaction energy between K and Be. Moreover, the dipole momentfunctions and transition dipole moments are also analyzed.The PECs, ro-vibrational levels and spectroscopic parameters have been calculated for1Π,3Π,1Σ+and3Σ+states of BAlk(Alk=Li, Na, K) employing the large all-electron basis setsdef2-AQZVPP-JKFI for Li, Na and K and aug-cc-PCV5Z for B. The effect of inner-shellelectrons are also taken into consideration. We find that3Σ+state of BAlk are all bound stateswhich are different from the results in the previous studies. The APEFs can accuratelyreproduce the interaction energy between B and Alk. The behaviors of the dipole moment forall the states as well as the TDMs from1Σ+to1Π and3Σ+to3Π state of BAlk molecules aredescribed.The reaction of Alkali-metal molecules system in ultracold temperature is moreinteresting than diatomic molecular. However, the dynamic research about Li2K is littlebecause there is no suitable potential energy surface. So, once studies on diatomic molecule,especially on KLi, completes successfully, we start to construct potential energy surface (PES)of Li2K which can help greatly in understanding such a system.43927energy points have been calculated for Li2K employing basis sets ECP10MDFfor Li, Na and K and aug-cc-pV5Z for Li.42000energy points, after analysis, were chosen tobe fitted. The many-body expansion and Aguado and Paniagua function were used toconstruct the APEFs. Then142parameters were obtained through nonlinear least-squaresalgorithm method. Based on the PES, we calculated the reaction cross-sections, correlationbetween vector k and k′, correlation between vector j and j′, correlation among vector k, k′and j′for different collision energies of K+Li2â†'KLi+Li using quasi-classical trajectory method. Some interesting results are found and we analyzed the results.