MRCI Calculation Of GuC And CuN Electronic State Structures

The high accuracy Ab initio calculation method-multireference configuration interaction (MRCI) has been used to calculate the diatomic electronic state structures of CuC and CuN. Considering the Davidson correction (+Q), the potential energy curves (PECs) for the low-lying excited states were obtained. Based on the PECs, the properties and spectral constants for the bound states were acquired through solving the one-dimension radial Schrodinger equation.In the CuC electronic state structure calculations, the four electronic states (2∑-2∏,4∑-, and 4∏) of CuC, corresponding to the lowest dissociation limits Cu(2Sg)+C(3Pg), were calculated by using multi-reference configuration interaction method with Davidson correction (MRCI+Q) approach. The calculation results indicate the ground state is 4∑-, but the first exciting state 2∏ has relatively low exciting energy with about 0.28eV. The calculation covers the internuclear distance ranging from 0.04 nm to 0.54 nm, and the equilibrium bond length Re, adiabatic excited energy Te and dissociation energy De are determined directly. With the potentials, all of the vibrational levels and rotational constants are predicted by numerically solving the radial Schrodinger equation of nuclear motion. We select the size of integral radial mesh to be 0.0001nm for solving the equation, and expanding the integral range to 0.04nm-0.99nm. There are 50,46,25, and 6 vibrational levels for the four bound state 4∑-,2∏,2∑- and 4∏, respectively. Then the spectroscopic constants of ωe, ωexe, Be, and ae are obtained after data fitting which are compared with theoretical results currently available. For the 4∑-,2∏,2∑-and 4∏ state, the harmonic vibrational frequencies ωe are 542.4cm-1,562.7 cm-1, 469.7 cm-1 and 569.1 cm-1, and the non-harmonic constant ωeXe are 3.77 cm-1,5.69 cm-1,10.68 cm-1 and 23.29cm-1, respectively.In the CuN electronic state structure calculations, the potential energy curves (PECs) of the X3∑-,13∏,23∑-,13△, 11△, 11∑-, 11∏, and5∑- in the range of R=0.1nm～0.5nm were scanned and which are goodly asymptote to the Cu(2Sg)+N(4Su) and Cu (2Sg)+N(2Du) dissociation limits. All the possible vibrational levels, rotational constant, and spectral constants for the six bound state of X3∑-,13∏,23∑-,11△,11∑-,and 1 1∏ were obtained by solving the radial Schrodinger equation of nuclear motion with Le Roy provided Leve18.0 program. Also the transition dipole moment from the ground state X3∑- to the excited state 13∏ and 23∑-were calculated and the result indicates that the 23∑--X3∑-transition has much higher transition dipole moment than the 13∏-X3∑-transition even though the 13∏ state is much low in energy than the 23∑-state. And the peak of the transition dipole moment for 23∑-X3∑- appears at R=0.25nm with D=4.76Debye, which is about 9 times larger than the 13∏-X3∑- transition.