Property-Optimized Gaussian Basis Sets for Lanthanides

Property-optimized Gaussian basis sets of split-valence, triple-zeta and quadruple-zeta valence quality are developed for the lanthanides Ce–Lu for use with small-core relativistic effective core potentials. They are constructed in a systematic fashion by augmenting def2 orbital basis sets with diffuse basis functions and minimizing negative static isotropic polarizabilities of lanthanide atoms with respect to basis set exponents within the unrestricted Hartree–Fock method. The basis set quality is assessed using a test set of 70 molecules containing the lanthanides in their common oxidation states and f electron occupations. 5d orbital occupation turns out to be the determining factor for the basis set convergence of polarizabilities in lanthanide atoms and the molecular test set. Therefore, two series of property-optimized basis sets are defined. The augmented def2-SVPD, def2-TZVPPD, and def2-QZVPPD basis sets balance the accuracy of polarizabilities across lanthanide oxidation states. The relative errors in atomic and molecular polarizability calculations are ≤8% for augmented split-valence basis sets, ≤2.5% for augmented triple-zeta valence basis sets, and ≤1% for augmented quadruple-zeta valence basis sets. In addition, extended def2-TZVPPDD and def2-QZVPPDD are provided for accurate calculations of lanthanide atoms and neutral clusters. The property-optimized basis sets developed in this work are shown to accurately reproduce electronic absorption spectra of a series of LnCp'3- complexes (Cp' = C5H4SiMe3, Ln = Ce–Nd, Sm) with time-dependent density functional theory.

DFT calculation of the Renner Teller Effect in NCO: Preliminary assessment of Exact Exchange Energy on the accuracy of the X2Π Renner Coefficient

Assessment of DFT methods through analysis of the Renner-Teller Effect (RTE) in the XΠ state of the NCO radical was completed. Our results suggest that the amount of exact exchange at long range is important for an accurate description of the RTE in NCO. DFT functionals from the B3LYP, PBE, TPSS, M06, and M11 families with standard Correlation Consistent, 6-311G split valence family, as well as Sadlej, and Sapporo polarized triple-ζ basis sets were assessed. Our Renner coefficients are compared with previously published theoretical and experimental results to characterize the overall accuracy of various functional/basis set combinations in determining the RTE splitting in the Π (bending) modes of NCO(XΠ). We suggest that this method of analysis can be extended to other systems, serve as an accuracy metric when selecting a functional, and provide a means to create training sets for machine learning in computational molecular physics applications.

Pairing double hybrid functionals with a tailored basis set for an accurate thermochemistry of hydrocarbons

The pairing of the PBE-QIDH double-hybrid functional with a tailored split-valence basis set leads to a fast computational protocol for the accurate evaluation of hydrocarbon thermochemistry, without resorting to any empirical correction.

Spin polarization in monolayer MoS2 in the presence of proximity-induced interactions

When monolayer (ML) MoS2 is placed on a substrate, the proximity-induced interactions such as the Rashba spin-orbit coupling (RSOC) and exchange interaction (EI) can be introduced. Thus, the electronic system can behave like a spintronic device. In this study, we present a theoretical study on how the presence of the RSCO and EI can lead to the band splitting, the lifting of the valley degeneracy and to the spin polarization in [Formula: see text]- and [Formula: see text]-type ML MoS2. We find that the maxima of the in-plane spin orientation in the conduction and valence bands in ML MoS2 depend on the Rashba parameter and the effective Zeeman field factor. At a fixed Rashba parameter, the minima of the split conduction band and the maxima of the split valence band along with the spin polarization in ML MoS2 can be tuned effectively by varying the effective Zeeman field factor. On the basis that the EI can be induced by placing the ML MoS2 on a ferromagnetic substrate or by magnetic doping in ML MoS2, we predict that the interesting spintronic effects can be observed in [Formula: see text]- and [Formula: see text]-type ML MoS2. This work can be helpful to gain an in-depth understanding of the basic physical properties of ML MoS2 for application in advanced electronic and optoelectronic devices.

Theoretical Coupling and Stability of Boronic Acid Adducts with Catecholamines

Background: Catecholamines combined with boric/boronic acids are attractive chemical agents in drug design because some of their adducts have shown interesting biological activity. Scant information exists about their stability. Objective: The aim of the present theoretical study was to explore the role of boron in molecules that combine catecholamines and boric/boronic acids, with a particular interest in examining stability. Method: The methodology was based on the US GAMESS program using DFT with the B3LYP exchange-correlation functional and the 6-31G (d,p) split-valence basis set. Results: According to the current findings, the boron-containing compounds (BCCs) exhibit weaker bonding to the hydroxyls on the ethylamine moiety than to those in the aromatic ring. The strongest binding site of a hydroxyl group was often found to be in meta-position (relative to ethylamine moiety) for boron-free compounds and in para-position for BCCs. Nonetheless, the methyl substituent in the amino group was able to induce changes in this pattern. We analyzed feasible boronsubstituted structures and assessed the relative strength of the respective C-B bonds, which allowed for the identification of the favorable points for reaction and stability. Conclusion: It is feasible to form adducts by bonding on the amine and catechol sides of catecholamines. The presence of boron stabilizes the adducts in para-position. Since some of these BCCs are promising therapeutic agents, understanding the mechanisms of reaction is relevant for drug design.

Исследование методом спектроскопии фотоотражения слоев LT-GaAs, выращенных на подложках Si и GaAs

The mechanical strains and densities of surface charge states in GaAs layers grown by low-temperature (LT) molecular-beam epitaxy on Si(100) and GaAs(100) substrates are investigated by photoreflectance spectroscopy. Lines corresponding to the fundamental transition ( E _ g ) and the transition between the conduction band and spin-orbit-split valence subband ( E _ g + Δ_ SO ) in GaAs are observed in the photoreflectance spectra of Si/LT-GaAs structures at 1.37 and 1.82 eV, respectively. They are shifted to lower and higher energies, respectively, relative to the corresponding lines in GaAs/LT-GaAs structures. Comparing the spectra of the Si/LT-GaAs and GaAs/LT-GaAs structures, it is possible to estimate mechanical strains in LT-GaAs layers grown on Si (by analyzing the spectral-line shifts) and the density of charge-carrier states at the GaAs/Si heterointerface (by analyzing the period of Franz–Keldysh oscillations).

COMPUTER-AIDED DESIGN OF OLED MATERIALS: A MOLECULAR MODELING APPROACH FOR OPTICAL PROPERTIES OF α-FLUORENYL OLIGOTHIOPHENES

Mono- and di-substituted α-fluorenyl oligothiophenes, FTn and FTFn (n is the number of thiophene units), have been investigated by efficient theoretical approaches, DFT and TDDFT with hybrid functional, B3LYP, and split valence plus polarization (SVP) basis set. The conjugation length was extended by increasing the number thiophene units up to pentamer (n = 1-5). According to our results, the structural and optical properties of these materials can be tuned by varying the number of thiophene units. We also reported a maximum absorption and a maximum emission of an ideal polymer which are in very good agreement with the experimental observation. It has, therefore, been demonstrated that TDDFT provides an accurate performance and can be one of the useful and affordable methods for future studies involving conjugated organic materials in OLEDs.