An investigation of density functionals: The first-row transition metal dimer calculations

Abstract

The performance of different density functional theory ͑DFT͒ methods was investigated in the calculations of the bond length and the binding energy of the first-low transition metal dimers. The 4s-3d interconfigurational energies and 4s and 3d ionization potentials were also calculated for the first-row transition metal atoms. In general, the hybrid DFT method, B3LYP, yields the bond lengths that are too short compared to the experimental ones. In contrast, the optimized bond lengths by nonhybrid DFT methods such as BOP or PW91 are in good agreement with the experiment. It was also found that nonhybrid DFT methods overestimate the binding energies, because they have a tendency to overstabilize the electron configurations that contain the atomic and molecular orbitals in a higher angular momentum open shell. The hybrid DFT method yields more accurate binding energies, but it estimates rather poor energy gaps between states whose spin multiplicity is quite different.

Quantum Monte Carlo study of the ground state and low-lying excited states of the scandium dimer

“…Focusing on ⌬E's, DMC predicts the 3 ⌺ u state and not the accepted 5 ⌺ u state to be the ground state, which is predicted to lie 0.17 eV higher in energy. B3LYP predicts the quintet to be the ground state, in accordance with previous DFT calculations, [16][17][18][19][20]58 only by 0.07 eV, however, as was observed for the atomic case, DMC results are more trustable than B3LYP for this case.…”

“…[16][17][18][19][20][21] In general, these studies predicted bond lengths in the range of 2.55-2.70 Å and frequencies that are in good agreement with the corresponding experimental marks. The calculated ionization energy of Sc was also in agreement with the experimental value of 6.56 eV.…”

Chemical Bonding and Electronic Properties of the Co Adatom and Dimer Interacting with Polyaromatic Hydrocarbons

“…104 Our calculated bond length for the ground state of the Co dimer is 1.96Å for both the S12g and PBE functionals, which is in between the experimental values obtained for the Fe 2 and Ni 2 112,113 and within the range of 1.95−2.41Å for different computational methods. [105][106][107][108][109] The effects of the spin-orbit coupling are also studied for the Co dimer using a full relativistic ZORA approach. The equilibrium bond distance is calculated for 1.96Å, as in the scalar relativistic approach, and the binding energy and IP are calculated to 2.48 and 6.83 eV, respectively, in agreement with the scalar ZORA approach.…”

Efficient algorithm for asymptotics-based configuration-interaction methods and electronic structure of transition metal atoms

“…Our results, detailed in Section VII below, provide an ab initio explanation of the anomalous magnetic moment of Chromium (experimentally, the ground state has six instead of the expected four aligned spins) and the underlying anomaly in the filling order of 3d versus 4s orbitals in the semi-empirical orbital picture of transition metal atoms (Chromium, unlike its four predecessors Ca, Sc, Ti, V, possesses only one instead of two 4s electrons). It is well known [11][12][13][14] that singledeterminant Hartree-Fock, relativistic Hartree-Fock, and density functional theory calculations (even with the best exchange-correlation functionals such as B3LYP) render the correct filling orders and ground state symmetries only for some but not all transition metal elements (see Section VII).…”