Prediction of spectroscopic constants for diatomic molecules in the ground and excited states using time‐dependent density functional theory

Abstract

Spectroscopic constants of the ground and next seven low-lying excited states of diatomic molecules CO, N2, P2, and ScF were computed using the density functional theory SAOP/ATZP model, in conjunction with time-dependent density functional theory (TD-DFT) and a recently developed Slater type basis set, ATZP. Spectroscopic constants, including the equilibrium distances r(e), harmonic vibrational frequency omega(e), vibrational anharmonicity omega(e)x(e), rotational constant B(e), centrifugal distortion constant D(e), the vibration-rotation interaction constant alpha(e), and the vibrational zero-point energy E(n)0 were generated in an effort to establish a reliable database for electron spectroscopy. By comparison with experimental values and a similar model with an established larger Slater-type basis set, et-QZ3P-xD, it was found that this model provides reliably accurate results at reduced computational costs, for both the ground and excited states of the molecules. The over all errors of all eight lowest lying electronic states of the molecules under study using the effective basis set are r(e)(+/-4%), omega(e)(+/-5% mostly without exceeding +/-20%), omega(e)x(e)(+/-5% mostly without exceeding 20%, much more accurate than a previous study on this constant of +/-30%), B(e)(+/-8%), D(e)(+/-10%), alpha(e)(+/-10%), and E(n)0(+/-10%). The accuracy obtained using the ATZP basis set is very competitive to the larger et-QZ3P-xD basis set in particular in the ground electronic states. The overall errors in r(e), omega(e)x(e), and alpha(e) in the ground states were given by +/-0.7, +/-10.1, and +/-8.4%, respectively, using the efficient ATZP basis set, which is competitive to the errors of +/-0.5, +/-9.2, and +/-9.1%, respectively for those constants using the larger et-QZ3P-xD basis set. The latter basis set, however, needs approximately four times of the CPU time on the National Supercomputing Facilities (Australia). Due to the efficiency of the model (TD-DFT, SAOP and ATZP), it will be readily applied to study larger molecular systems.

Density functional theory calculation of 2p spectra of SiH4, PH3, H2S, HCl, and Ar

“…The overall agreement with experiment is not bad, although the occasional discrepancies of ca. 1 eV are considerably larger than what has been found in other TD-DFT calculations of valence excitation energies using SAOP [15,22,39,40,45]. Each molecule has its own characteristic spectrum.…”

“…We have demonstrated that TD-DFT with the SAOP exchange-correlation potential can predict reliable vertical excitation energies [15,22,39,40].…”

Formation and Characterization of the Boron Dicarbonyl Complex [B(CO)2]−

“…2 in the molecule. [8] Therefore,C Ob inds preferentially through donor-acceptor interactions A!B. [7] Thed ifferent bonding situation compared with linear allene H 2 C=C=CH 2 ,w hich has ad eep potential well, can be rationalized with the 3 B 1 triplet ground state of CH 2 ,which preferentially engages in normal covalent ("electron-sharing") bonds A À B.…”

Spectroscopic constants and molecular properties of A3Σu+, B3Πg, W3Δu, and B′3Σu− electronic states of the N2 molecule

“…In addition, two of the excited electronic states, B 3 Π g and W 3 Δ u , are of special interest, because their potential energy curves (PECs) nearly coincide and thus give rise to peculiar spectral behavior 4. Therefore, the spectroscopic and molecular properties of the N 2 have become the subject of extensive studies in the past several decades, both experimentally 1–3, 5–11 and theoretically 4, 12–27.…”