Melchiorsensantos1700

Atomic layer deposition (ALD) is a powerful tool for achieving atomic level control in the deposition of thin films. However, several physical and chemical phenomena can occur which cause deviation from "ideal" film growth during ALD. Understanding the underlying mechanisms that cause these deviations is important to achieving even better control over the growth of the deposited material. Herein, we review several precursor chemisorption mechanisms and the effect of chemisorption on ALD growth. We then follow with a discussion on diffusion and its impact on film growth during ALD. Together, these two fundamental processes of chemisorption and diffusion underlie the majority of mechanisms which contribute to material growth during a given ALD process, and the recognition of their role allows for more rational design of ALD parameters.We present a simple method for a posteriori removal of a significant fraction of the density-fitting error from the calculated total coupled-cluster energies. The method treats the difference between the exact and density-fitted integrals as a perturbation, and simplified response-like equations allow us to calculate improved amplitudes and the corresponding energy correction. The proposed method is tested at the coupled-cluster singles and doubles level of theory for a diverse set of moderately-sized molecules. On average, error reductions by a factor of approximately 10 and 20 are observed in double-zeta and triple-zeta basis sets, respectively. Similar reductions are observed in calculations of interaction energies of several model complexes. The computational cost of the procedure is small in comparison with the preceding coupled-cluster iterations. The applicability of this method is not limited to the density-fitting approximation; in principle, it can be used in conjunction with an arbitrary decomposition scheme of the electron repulsion integrals.We present an algorithm for efficient calculation of analytic nonadiabatic derivative couplings between spin-adiabatic, time-dependent density functional theory states within the Tamm-Dancoff approximation. check details Our derivation is based on the direct differentiation of the Kohn-Sham pseudowavefunction using the framework of Ou et al. Our implementation is limited to the case of a system with an even number of electrons in a closed shell ground state, and we validate our algorithm against finite difference at an S1/T2 crossing of benzaldehyde. Through the introduction of a magnetic field spin-coupling operator, we break time-reversal symmetry to generate complex valued nonadiabatic derivative couplings. Although the nonadiabatic derivative couplings are complex valued, we find that a phase rotation can generate an almost entirely real-valued derivative coupling vector for the case of benzaldehyde.The influence of the nuclear magnetization distribution effects on the hyperfine structure of electronic states of thallium atom is studied within the relativistic coupled cluster theory. Relative significance of these effects is demonstrated for the first excited electronic state 6P3/2 of neutral Tl. Based on the obtained theoretical and available experimental data, the nuclear magnetic moments of short-lived 191Tlm and 193Tlm isotopes are predicted μ191 = 3.79(2) μN and μ193 = 3.84(3) μN, respectively. Using theoretical and experimental data for the neutral Tl, the magnetic anomalies 205Δ203 for the 7S1/2 state of the neutral Tl atom and the 1S1/2 state of the hydrogen-like ion are also predicted.There have been several reports of plasmonically enhanced graphene photodetectors in the visible and the near infrared regime but rarely in the ultraviolet. In a previous work, we have reported that a graphene-silver hybrid structure shows a high photoresponsivity of 13 A/W at 270 nm. Here, we consider the likely mechanisms that underlie this strong photoresponse. We investigate the role of the plasmonic layer and examine the response using silver and gold nanoparticles of similar dimensions and spatial arrangement. The effect on local doping, strain, and absorption properties of the hybrid is also probed by photocurrent measurements and Raman and UV-visible spectroscopy. We find that the local doping from the silver nanoparticles is stronger than that from gold and correlates with a measured photosensitivity that is larger in devices with a higher contact area between the plasmonic nanomaterials and the graphene layer.The Bethe-Salpeter equation (BSE) based on GW quasiparticle levels is a successful approach for calculating the optical gaps and spectra of solids and also for predicting the neutral excitations of small molecules. We here present an all-electron implementation of the GW+BSE formalism for molecules, using numeric atom-centered orbital (NAO) basis sets. We present benchmarks for low-lying excitation energies for a set of small organic molecules, denoted in the literature as "Thiel's set." Literature reference data based on Gaussian-type orbitals are reproduced to about one millielectron-volt precision for the molecular benchmark set, when using the same GW quasiparticle energies and basis sets as the input to the BSE calculations. For valence correlation consistent NAO basis sets, as well as for standard NAO basis sets for ground state density-functional theory with extended augmentation functions, we demonstrate excellent convergence of the predicted low-lying excitations to the complete basis set limit. A simple and affordable augmented NAO basis set denoted "tier2+aug2" is recommended as a particularly efficient formulation for production calculations. We finally demonstrate that the same convergence properties also apply to linear-response time-dependent density functional theory within the NAO formalism.Continued interest regarding the rheometric measurements of molten sulfur has persisted due to the need for industrial-scale transportation and handling of the material in a liquid phase. This has allowed for extended research developments to attain a fundamental understanding of the fluid. This work reports novel high temperature modulus data over the λ-transition region for liquid elemental sulfur, measured through the use of a modified Anton-Paar Modular Compact Rheometer 302. From these measurements, further insight was gained on the viscoelastic behavior and reptative relaxation times for liquid elemental sulfur. The slow relaxation time, τs, related to reptative behavior, was found to be between 0.24 s and 0.28 s at 190 °C. Utilizing the Maxwell relation, this was determined to correspond to an estimated viscosity range from 72 000 × 10-3 Pa s to 95 000 × 10-3 Pa s, which is in agreement with previous viscosity studies on liquid sulfur. A Cole-Cole plot of the experimental data also displayed characteristics of Debye-like relaxation, suggesting that the slow relaxation process was related to local S-S bond scission and recombination in sulfur chains and was not a relaxation coinciding with a polymeric chain mode.