Electronic Excitations in Transition Metal Dioxide and Open-Shell Molecular Systems

Many-body perturbation within the GW approximation is a powerful method to calculate the electron removal and addition energies in a wide variety of bulk and molecular systems. Over the last decade, there have been an increasing number of studies that have benchmarked the performance of this method in molecular systems. Most of these studies have focused on closed-shell and sp-bonded molecules. In this thesis, I investigate the performance of different flavors of the GW approximation in two systems: (i) negatively charged 3d-transition metal dioxide molecules, and (ii) systems that exhibit multiplet splitting in their photoelectron spectra. These are systems of both technological and scientific interest, and they present significant computational challenges for straightforward application of GW methods due to enhanced electron correlations and their open-shell character. For the first system, I present results and analyses of photoelectron spectra of early 3d-transition metal dioxide molecular anions TMO2- (TM = Sc, Ti, V, Cr, Mn) computed using semi-local and hybrid density functional theory (DFT) and the GW approximation with perturbative and eigenvalue self-consistent formalisms. The results are compared with each other and with experimental photoelectron spectroscopy data. I show that perturbative GW with a particular fraction of exact exchange (25%) on top of Perdew-Burke-Ernzerhof exchange-correlation functional provides excellent agreement with experiment by mitigating self-interaction error. I also show that an eigenvalue self-consistent formalism with updates in the Green’s function is a reasonably accurate choice for computing electron removal energies. In the second project, I investigate the performance of two different perturbative GW approaches with hybrid functional DFT starting points for five sp-bonded open-shell molecules, NO2, NF2, ClO2, O2, and S2, containing multiplet-split orbitals in their photoelectron spectra. My results show that (i) typical semi-local exchange-correlation functionals do not provide good agreement with experimental data for multiplet-split orbitals, and (ii) it is possible to accurately predict multiplet splitting in open-shell molecules by adding a fraction of exact exchange in the DFT starting point

Artificial recharge efficiency assessment by soil water balance and modelling approaches in a multi-layered vadose zone in a dry region

<p>To assess recharge through floodwater spreading, three wells, approx. 30 m deep, were dug in a 35-year-old basin in southern Iran. Hydraulic parameters of the layers were measured. One well was equipped with pre-calibrated time domain reflectometry (TDR) sensors. The soil moisture was measured continuously before and after events. Rainfall, ponding depth and the duration of the flooding events were also measured. Recharge was assessed by the soil water balance method, and by calibrated (inverse solution) HYDRUS-1D. The results show that the 15 wetting front was interrupted at a layer with fine soil accumulation over a coarse layer at the depth of approx. 4 m. This seemed to occur due to fingering flow. Estimation of recharge by the soil water balance and modelling approaches showed a downward water flux of 55 and 57% of impounded floodwater, respectively.</p

Physiological Temperature Has a Crucial Role in Amyloid Beta in the Absence and Presence of Hydrophobic and Hydrophilic Nanoparticles

Amyloid beta fibrillation can lead to major disorder of neurons processes and is associated with several neuronal diseases (e.g., Alzheimer’s disease). We report here an importance of slight temperature changes, in the physiological range (35–42 °C), on the amyloid fibrillation process in the presence and absence of hydrophilic (silica) and hydrophobic (polystyrene) nanoparticles (NPs). The results highlight the fact that slight increases in temperature can induce inhibitory and acceleratory effects of hydrophobic and hydrophilic NPs on the fibrillation process, respectively. Using further in vivo considerations, the outcomes of this study can be used for considerable modifications on the current diagnosis and treatment approaches in amyloid-involved diseases

Temperature: The “Ignored” Factor at the NanoBio Interface

Upon incorporation of nanoparticles (NPs) into the body, they are exposed to biological fluids, and their interaction with the dissolved biomolecules leads to the formation of the so-called protein corona on the surface of the NPs. The composition of the corona plays a crucial role in the biological fate of the NPs. While the effects of various physicochemical parameters on the composition of the corona have been explored in depth, the role of temperature upon its formation has received much less attention. In this work, we have probed the effect of temperature on the protein composition on the surface of a set of NPs with various surface chemistries and electric charges. Our results indicate that the degree of protein coverage and the composition of the adsorbed proteins on the NPs’ surface depend on the temperature at which the protein corona is formed. Also, the uptake of NPs is affected by the temperature. Temperature is, thus, an important parameter that needs to be carefully controlled in quantitative studies of bionano interactions