A Theoretical Study on the Excited States of the KCCH Radical

Haifeng Zhang,Xiaodong Zhao,Jiubo Cui,Xuetong Zhu,Yunfei Wu,Weiwei Pei,W Qin,L Wang,V Yepes

doi:10.1051/e3sconf/202016505030

Abstract

Based on the C2v symmetry, the low-lying electronic states of the KCCH radical was studied in the complete active pace self-consistent field (CASSCF) and multi-configurational second-order perturbation theory (CASPT2) methods. For the low-lying electronic states of KCCH, the calculated harmonic vibrational modes are in agreement with theoretical reports. Moreover, the electron transitions of KCCH, from X1Σ+ to 21Σ+, 11Π, 21Π, 11Σ-, 13Σ+, 13Π, 23Π and 13Σ-, are predicted at 5.43, 5.59, 7.87, 5.50, 5.15, 5.73, 5.53 and 6.82 eV, respectively. The CASSCF/CASPT2 potential energy curves (PECs) were calculated for K+-loss dissociation from the 13Σ+, 23Σ+,13Π ,21Σ, 11Π and 21Π states. Analyses of electron transition and dissociation curves show the ionic properties in the metal–ligand bond for KCCH. The dissociation energy of the KCCH (X1Σ+)→CCH-(11Σ)+K+(S0) is 4.423 eV at the CASSCF/CASPT2 level.

Highlights

Over the past 30 years, the investigations for the metal monoacetylides have been progressed steadily, which include both theory and experiment, and have focused mainly on the alkali and alkaline-earth metals
Calculations were performed by means of the CASSCF and CASPT2 methods, using the VDZP and VTZP basis electronic configuration of(10σ)2(3πx)2(3πy)2 with the coefficient of -0.95 at the X1Σ+ state is shown in sets of ANO-RCC
We reported a combined CASSCF and CASPT2 study of the low-lying electronic states of the KCCH radical in C2v symmetry for the first time

Summary

Introduction

Over the past 30 years, the investigations for the metal monoacetylides have been progressed steadily, which include both theory and experiment, and have focused mainly on the alkali and alkaline-earth metals. The structure of alkali metal monomeric KCCH has been determined by means of millimeter/submillimeter rotational spectroscopy and Fourier transform microwave (FTMW) spectroscopy in the different frequency ranges[2,3]. With these precise experimental results given, an opportunity is offered for an updated theoretical investigation by means of ab initio quantum chemical methods. Scalmani et al had investigated the electronic properties of the molecule by means of a variety of theoretical models ranging from semiempirical techniques to Hartree–Fock (HF-SCF) and standard postHF methods and a number of density functional theory (DFT) techniques[5]. J. et al had calculated the equilibrium structure of KCCH using the coupled-cluster singles and doubles (CCSD) approach[6]

Methods

Results

Conclusion