RESUMO

Identifying and manipulating spin in two-dimensional materials is of great interest in advancing quantum information and sensing technologies, as well as in the development of spintronic devices. Here, we investigate the influence of hydrogen adsorption on the electronic and magnetic properties of graphene-like triangulenes. We have constructed triangulenes from SiC monolayers, which have been successfully synthesized very recently, extending our investigation to include graphene triangulenes. This advancement in the synthesis of SiC monolayers allows us to investigate deeper into the unique properties of SiC-based triangulenes and compare them with their graphene counterparts. The addition of hydrogen has been found to induce a magnetic moment in the SiC monolayer, with a more localized spin density when H is adsorbed in the C sites while spreading through the lattice when adsorbed on the Si sites. In triangular flakes, the ground spin state changes with the adsorption site: decreasing multiplicity on edge-defined sublattices and increasing it on the opposite sublattice. These findings suggest hydrogen adsorption as a tool for tuning spin-state properties in SiC and graphene nanostructures, with potential applications in spintronics and spin quantum dot devices.

RESUMO

Using density functional theory at D3-B3LYP/aug-cc-pVDZ level combined with the conductor-like polarizable continuum model (CPCM) solvent model, a study of the IR spectrum of H 2 O $$ {\mathrm{H}}_2\mathrm{O} $$ :HCN mixtures is reported. The CPCM solvent effect notably enhances the accuracy of the IR spectra compared to gas-phase calculations, while the dielectric constant value has minimum impact on the final spectrum. An optimized methodology is suggested that effectively minimizes the root mean square deviation between theoretical and experimental data. This novel approach not only enhances the quality of the final IR spectra but also captures relevant spectral features, highlighting its potential to decipher molecular interactions in such intricate mixtures.

RESUMO

Two variants of a successive quadratic minimization method (SQM and c-SQM) are suggested to calculate the structural properties of molecular systems at the complete basis set (CBS) limit. When applied to H3+, H2O, CH2O, SH2, and SO2, they revealed CBS/(x1, x2) structural parameters that significantly surpass the raw ones calculated at the x2 basis set level. Such a performance has also been verified for the intricate case of the water dimer. Because the c-SQM method is system specific, thus showing somewhat enhanced results relative to the general SQM protocol, it can be of higher cost depending on the level of calibration used. Yet, it hardly surpasses the general quality of the results obtained with the cost-effective SQM method. Since the number of cycles required to reach convergence is relatively small, both schemes are simple to use and easily adaptable to any of the existing extrapolation schemes for the Hartree-Fock and correlation energies.

RESUMO

AIMS: To report toxicity of a hypofractionated scheme of whole-breast (WB) intensity-modulated radiotherapy (IMRT) with simultaneous integrated boost (SIB) to the tumor bed (TB) using Tomotherapy® with Direct modality. METHODS: Patients with early breast cancer, undergoing radiotherapy (RT) in 15 daily fractions to WB (prescription dose 40.05 Gy) and SIB to the TB (48 Gy), between 2013 and 2017, was analyzed. Primary endpoint was acute and intermediate toxicity assessed at the end and within 6 months from RT, according to Radiation Therapy Oncology Group (RTOG) scale. Secondary endpoints included early chronic toxicity at 12-months follow-up, using the Late Effects Normal Tissue Task Subjective, Objective, Management, and Analytic (LENT-SOMA) scale, and cosmesis using Harvard criteria. RESULTS: The study population was of 287 patients. Acute and intermediate toxicity was collected among 183 patients with data available at the end of RT and within 6 months, 85 (46%) experienced G2 toxicity and 84 (46%) G1 toxicity, while 14 (8%) did not report toxicity at any time. A significant reduction of any grade toxicity was observed between the two time points, with the majority of patients reporting no clinically relevant toxicity at 6 months. At univariate analysis, age < 40 years, breast volume > 1000 cm3 and Dmax ≤ 115% of prescription dose were predictive factors of clinically relevant acute toxicity (G ≥ 2) at any time. At multivariable analysis, only age and breast volume were confirmed as predictive factors, with Relative Risks (95% Confidence Intervals): 2.02 (1.13-3.63) and 1.84 (1.26-2.67), respectively. At 12-month follow-up, 113 patients had complete information on any toxicity with 53% of toxicity G < 2, while cosmetic evaluation, available for 102 patients, reported a good-excellent result for 86% of patients. CONCLUSIONS: Hypofractionated WB IMRT with a SIB to the TB, delivered with TomoDirect modality, is safe and well-tolerated. Most patients reported no toxicity after 6 months and good-excellent cosmesis. Predictive factors of clinically relevant toxicity might be considered during treatment planning in order to further reduce side effects.

Assuntos

Neoplasias da Mama/radioterapia , Hipofracionamento da Dose de Radiação , Radioterapia de Intensidade Modulada/efeitos adversos , Doença Aguda , Adulto , Idoso , Neoplasias da Mama/patologia , Feminino , Humanos , Pessoa de Meia-Idade , Estudos Prospectivos , Lesões por Radiação/etiologia , Radioterapia de Intensidade Modulada/métodos , Fatores de Tempo

RESUMO

A detailed analysis of the electronic structure of the ground and first excited spin state of three diatomic molecules ( N2, BH and CO) under static applied electric field is performed at CCSD(T), DFT, MRCI and MRCI(Q) levels of theory. Our findings have revealed that by boosting the applied field one induces changes in the occupation numbers of molecular orbitals, giving rise to changes in the equilibrium geometry and in the HOMO-LUMO energy gap. Specifically, singlet to triplet spin transition can be induced by increasing the applied electric field beyond a critical value. Accordingly, affecting the accuracy of the widely used expression of energy expanded in Taylor series with respect to the applied electric field. © 2018 Wiley Periodicals, Inc.

RESUMO

In this paper, an augmented all-electron double-ζ basis set is used in calculations of the structure and electronic properties of small niobium clusters. The B3PW91 and M06 DFT functionals with and without second order Douglas-Kroll-Hess (DKH) scalar relativistic corrections are also utilized. Furthermore, an additional d Gaussian type function is introduced in the standard basis sets in order to improve the description of the clusters orbitals in the valence band. Our findings show that the extra d function is important to yield accurate results of electronic properties and, in addition, the DKH corrections can be relevant when the all-electron basis sets are used in the calculations. Our best results are obtained with the M06 functional together with the DKH second order corrections and with the extra d function added to the all-electron basis set.

RESUMO

A method previously suggested to calculate the correlation energy at the complete one-electron basis set limit by reassigning the basis hierarchical numbers and using the unified singlet- and triplet-pair extrapolation scheme is here utilized to extrapolate tensorial properties, with specific use for the polarizabilities of eight molecules whose raw values are obtained with second-order Møller-Plesset perturbation theory and coupled-cluster singles and doubles excitation methods, both without and with inclusion of the perturbative triples correction. Good agreement is obtained with the best available estimates even when the (d, t) pair of hierarchical numbers is utilized to perform the extrapolations. This conceivably reinforces our previous finding that there is no good reason to exclude double-ζ results in extrapolations, especially if the basis is calibrated to comply with the theoretical model.