Effect of Initial Configuration on DFT Calculations for Transition Metal Complexes

Computational methods, which solves the Schrödinger’s equation for molecules, have become an indispensable tool in last decades. And Density Functional Theory is one of the most used, and most effective computational method. Transition Metal complexes, on the other hand, have been being used extensively in many important applications in many fields, such as chemical catalysts, atomic thin films, and pharmaceutical industry. Applying computational methods to transition metal complexes has become inevitable to understand better, to control and to design these compounds. As it is known, it is very difficult to handle transition metals computationally, mostly due to near degeneracy in their electronic states. The computational algorithms usually cannot achieve as successive result as they can do for other typical elements, like carbon or nitrogen for instance. Computational methods are needed to be improved for properly deal with transition metal complexes. To find computationally cheaper but still effective methods to deal with these complexes is a major challenge. Unlike the analogue calculations, computational methods solve all equations iteratively, so there are major differences between these two calculation types. The starting point in state space (the assumed initial conformation of molecule) is could have a stronger effect then the expected, on the flow of the iterative solving algorithm of the computational approach. Here we present a comparative study for a Ruthenium complex. We have optimised the molecule several times. Each of the optimisations started from different initial molecular conformations. Then we have compared the result in different ways, like calculation times and minimum energy that had reached, to see effect of starting configurations on the calculation. It is showed that, starting configuration is an important parameter for computational calculations of transition metal complexes, and it is needed to be carefully chosen to improve success of calculations

Quantıtıve Rısk Assesment Of Subsea Pıpelıne Instabılıty And Desıgn

Bu tez çalışmasında, deniz tabanındaki boruların hem düşeydeki hem de yataydaki yer değiştirme risk seviyelerinin değerlendirilmesi yapılmıştır. Modelleme çalışmasında, deniz tabanı topoğrafyasının, hidrodinamik yüklerin, boru-zemin etkileşiminin, dalgaların ve akıntının borular üzerindeki etkileri ve risk değerlendirmesi örnek uygulamalar üzerinde yapılmıştır. Boruların darbelere karşı risk seviyeleri için, uygulamada kullanılan Det Norske Veritas (DNV) standartlarına göre yeni seviye önerileri sunulmuştur. Bu çalışmadaki amaç, literatürdeki diğer çalışmalardan farklı olarak deniz tabanındaki boruların hem düşeyde hem de yataydaki yer değiştirme risklerini değerlendirerek, boruların taşıdığı farklı hammaddelerin boru dengesi üzerine olan etkisini ortaya koymaktır. Ayrıca bu çalışmada, boru et kalınlıklarının güvenirlik üzerine etkisi hassasiyet analizi ile irdelenmiştir. Bu çalışmada endüstriyel boyutlu boruların tasarımına yönelik olup güvenilirliğe dayalı tasarımını içermektedir. Literatürdeki risk analizlerinde riskin seviyesi DNV-RP-H101 standardında düşük, orta ve yüksek risk seviyesi olmak üzere tanımlanmıştır. Belirtilen standartlarda daha çok zemin ve boru etkileşimi üzerinde durulurken, bu tez çalışmasında dalga ve akıntı etkisi birlikte irdelenmiştir. Bu tez çalışmasının özgün yönü, dalga parametrelerine bağlı olarak risk seviyelerinin irdelenmesi ve yıllık yıkılma olasılığının Türkiye'den bir saha uygulaması ile desteklenmesidir. Limit durum fonksiyonlarının MCB ile bulunan kesinlik değeri olasılığı denge durum yüzeyinin altında kalan bölgeyi tanımladığından yıllık yıkılma olasılığını vermektedir. Bu tez çalışması sonucundaki önerim, boru sistemlerinin bütünü düşünüldüğünde, MCB sonucunda bulunan olasılığın tanım olarak borunun münferit olarak yer değiştirmesini, başka bir deyişle deplasman limitinin aşılma olasılığını ifade etmesidir.The assesment of displacement levels of both the vertical and horizontal displacements of the submarine pipeline has been done. In this modelling study, the effects of subsea topography, hydrodynamic loads, pipe-soil interaction, the effects of waves and currents on the pipeline, and the risk assesment were made on sample applications. A new level of proposal has been presented for impact risk levels of pipes in accordance with the Det Norske Veritas (DNV) standards used in practice. The risk assessment of the risk levels is examined in detail. The aim of this study is to evaluate the risk of displacement of both the vertical and horizontal displacements of the offshore pipeline, as well as the effects of the different raw materials carried by the pipeline on the pipeline balance, unlike other studies in the literature. In addition, in this study, the effect of pipe wall thickness on reliability was examined by sensitivity analysis. The effect of wave and current is investigated together while emphasizing the soil and pipe interaction in the above mentioned standards and applied in this thesis study. The thesis has a specific aspect with respect to study of risk levels depending on wave parameters and is supported by a field application than Turkey's annual probability of failure. The likelihood probability of limit state functions with MCB defines the region below the equilibrium state, thus giving the possibility of annual failure. The conclusion of this thesis study is that the probability that the MCB result is considered as the whole of the piping system is defined as the displacement of the pipe individually, in other words, the probability of exceeding the displacement limit

Summarizing Data Sets for Data Mining by Using Statistical Methods in Coastal Engineering

Coastal regions are the one of the most commonly used places by the natural balance and the growing population. In coastal engineering, the most valuable data is wave behaviors. The amount of this data becomes very big because of observations that take place for periods of hours, days and months. In this study, some statistical methods such as the wave spectrum analysis methods and the standard statistical methods have been used. The goal of this study is the discovery profiles of the different coast areas by using these statistical methods, and thus, obtaining an instance based data set from the big data to analysis by using data mining algorithms. In the experimental studies, the six sample data sets about the wave behaviors obtained by 20 minutes of observations from Mersin Bay in Turkey and converted to an instance based form, while different clustering techniques in data mining algorithms were used to discover similar coastal places. Moreover, this study discusses that this summarization approach can be used in other branches collecting big data such as medicine

Benzylation of benzene and toluene with benzylchloride over clay-based acid catalysts

The pillared clay catalysts were calcined after in corporation of metal polycation ions with exchangeable cations and water. Friedel-Crafts alkylations of aromatic hydrocarbons were carried out in the presence of clay catalysts originating from bentonite. In these reactions, it has been found that pillared clays have excellent catalytic activity. It was found that iron pillared clay (Fe-PILC) was the more efficient catalyst producing quantitative conversion with greatly reduced amounts of catalysts in short reaction period. Their efficiency is attributed to the higher Fe3+, Cr3+ and Al 3+ contents in the catalysts and pillaring effect. The clays have both Bronsted and Lewis acidities which were determined by pyridine adsorption-desorption and in situ FTIR technique

Zeolite confined copper(0) nanoclusters as cost-effective and reusable catalyst in hydrogen generation from the hydrolysis of ammonia-borane

Herein we report the development of a cost-effective nanocluster catalyst for the hydrolytic dehydrogenation of ammonia-borane which is considered to be one among the new hydrogen storage materials. Zeolite confined copper(0) nanoclusters were prepared by the ion-exchange of Cu2+ ions with the extra framework Na+ ions in zeolite-Y followed by reduction of the Cu2+ ions within the cavities of zeolite with sodium borohydride in aqueous solution and characterized by HR-TEM, XRD, XPS, SEM, EDX, ICP-OES, Raman spectroscopy and N-2 adsorption-desorption technique. Zeolite confined copper(0) nanoclusters are found to be active catalysts in the hydrolysis of ammonia-borane even at low temperatures (<= 15 degrees C) and stable enough for being isolated as solid materials. They provide 1300 turnovers in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. The average value of turnover frequency is 46.5 h(-1) for the same reaction. More importantly, zeolite confined copper(0) nanoclusters were found to be isolable, bottleable and reusable catalysts in the hydrolytic dehydrogenation of ammonia-borane; even at fifth run the complete release of hydrogen from the hydrolysis of ammonia-borane at room temperature is achieved. The work reported here also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy and the effect of catalyst concentration on the rate for the catalytic hydrolysis of ammonia-borane. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved

Water soluble laurate-stabilized ruthenium(0) nanoclusters catalyst for hydrogen generation from the hydrolysis of ammonia-borane: High activity and long lifetime

The simplest amine-borane, considered as solid hydrogen storage material, ammonia-borane (H(3)NBH(3)) can release hydrogen gas upon catalytic hydrolysis under mild conditions. Herein, we report the preparation of a novel catalyst, water dispersible laurate-stabilized ruthenium(0) nanoclusters from the dimethylamine-borane reduction of ruthenium(III) chloride in sodium laurate solution at room temperature. The ruthenium nanoclusters in average size of 2.6 +/- 1.2 nm were isolated from the solution and well characterized by using TEM, XPS, FTIR, and UV-visible electronic absorption spectroscopy, The water dispersible laurate-stabilized ruthenium(0) nanoclusters were found to be highly active and long-live catalyst with a TOF of 75 mol H(2)/mol Ru.min and TTO value of 5900 mol H(2)/mol Ru in the hydrolysis of ammonia-borane at 25.0 +/- 0.1 degrees C.(C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved

Water soluble laurate-stabilized rhodium(0) nanoclusters catalyst with unprecedented catalytic lifetime in the hydrolytic dehydrogenation of ammonia-borane

Herein we report, for the first time, the preparation and characterization of water soluble rhodium(0) nanoclusters stabilized by laurate (dodecanoate) anion and their catalytic activity in the hydrolysis of ammonia-borane. The water soluble laurate-stabilized rhodium(0) nanoclusters were prepared from the reduction of rhodium(III) chloride by dimethylamine-borane in solution containing sodium laurate at room temperature. The water soluble laurate-stabilized rhodium(0) nanoclusters in average size of 5.2 +/- 2.7 nm could be isolated from the reaction solution and characterized by using UV-vis, TEM, XPS, XRD and FTIR spectroscopic methods. Catalytic activity of rhodium(0) nanoclusters was tested in the hydrolysis of ammonia-borane. They show exceptional catalytic activity and unprecedented catalytic lifetime in this reaction. They provide a TOF value of 200 mol H-2/mol Rh min and 80,000 turnovers in the hydrolysis of ammonia-borane in air at 25.0 +/- 0.1 degrees C