Modeling the Photoelectron Spectra of MoNbO₂^– Accounting for Spin Contamination in Density Functional Theory

Abstract

Spin contamination in density functional studies has been identified as a cause of discrepancies between theoretical and experimental spectra of metal oxide clusters such as MoNbO2. We perform calculations to simulate the photoelectron spectra of the MoNbO2 anion using broken-symmetry density functional theory incorporating recently developed approximate projection methods. These calculations are able to account for the presence of contaminating spin states at single-reference computational cost. Results using these new tools demonstrate the significant effect of spin-contamination on geometries and force constants and show that the related errors in simulated spectra may be largely overcome by using an approximate projection model.

Linear polarizabilities and second hyperpolarizabilities of streptocyanines: Results from broken‐Symmetry DFT and new CCSD(T) benchmarks

“…Since the chemical structure of the streptocyanine system is composed of successive single‐double carbon–carbon bonds, the π orbitals are much more strongly conjugated along the backbone. Furthermore, from a more theoretical standpoint, a lower‐energy broken‐symmetry configuration is more favored if the DFT method contains a higher percentage of HF exchange (such as range‐separated functionals with large values of ω ). It is also interesting to note that only the streptocyanine oligomers with more than 4 monomer units will exhibit broken‐symmetry configurations where the alpha and beta spin densities alternate through the whole backbone of the molecule when ω is sufficiently large.…”

On the Linear Geometry of Lanthanide Hydroxide (Ln—OH, Ln=La-Lu)

“…26 Similar studies performed on AnC2 and AnCl3 have also implicated actinide 5f orbitals in bond formation. [26][27][28][29][30][31][32] Motivated by our lab's recent interest in metal oxide clusters, [33][34][35][36][37][38] we were intrigued by an apparent dearth of literature exploring the structure and bonding of lanthanide hydroxides. With the goal of exploring the full series, we note the inclusion of PmOH; while included here for completeness, Pm is unstable and thus PmOH is not likely to be experimentally studied.…”

Polarizabilities of π-Conjugated Chains Revisited: Improved Results from Broken-Symmetry Range-Separated DFT and New CCSD(T) Benchmarks

“…separated functionals with higher values of µ inherently contain larger contributions of HF exchange in the XC potential, and it is well-known 44-48 that DFT methods containing a large percentage of HF exchange will favor a lower-energy, broken-symmetry configuration [44][45][46][47][48]. It is interesting to note that for sufficiently large values of µ, all PBT oligomers (even the smallest PBT[2] structure) will exhibit a broken-symmetry solution where the alpha and beta spin densities alternate through the whole backbone of the molecule, and a long-range ordering of the spin density persists as the length of the oligomer increases.…”