Abstract We have performed ab initio molecular-dynamics (MD) calculations for the dependence of the sticking property of a C gas-phase atom ( ) on C(100) on the initial velocity. We have considered initial velocities of 0.0082, 0.0117 and 0.0185 . The largest velocity considered corresponds to a kinetic energy of 0.2142 eV, which is comparable with the chemisorption energy of an order of 1eV. For the three initial velocities considered, can settle on C(100) easily. The relatively quick settlement of even with a large initial velocity can be attributed to an efficient transfer of kinetic energy from to the H atom. We also find that the higher initial velocity, the deeper penetrates into the substrate, which renders to stay closer to the impact position.

The objectives of this work are to discuss multiscale models that are used to characterize the constitutive relations of the granular composite materials with dual functions. This is accomplished by the use of ab initio methods to obtain the constitutive relations of the structural energetic materials without conducting tests. First, it is necessary to study the quantum many body problem to quantitatively determine the internal energy of the material when subjected to different strain conditions. It is impossible to obtain an exact solution to the quantum many body problem that is modeled by the Schrödinger's equations with the current technology. It is possible to solve these equations approximately by the density functional theory which yields only energies at absolute 0ºK. Thus it becomes necessary to add both the lattice thermal contributions and electron thermal contribution. Then, resulting energy is used to bridge to the continuum level and obtain the constitutive equations. This is the procedure that is used in this work. The issues of the constitutive equations form the focus of this thesis. More specifically, the scope of the thesis is further restricted to analyze the constitutive equations of specific mixtures of nickel, aluminum with PTFE or Teflon as the binder. It is to be noted that the equations of state forms only a part of the complete constitutive relationships. This thesis presents solutions to the following problems: (1) Determination of the thermodynamically complete equation of state of the binder and the energetic material PTFE or Teflon, from ab initio methods based on the density functional theory. (2) Determination of the equations of state of the granular composite or the mixture of nickel, aluminum and PTFE from ab initio methods. (3) Determination of the complete constitutive equation of aluminum, from ab initio methods, under conditions of finite deformations, with principle of objectivity, material symmetry conditions and polyconvexity of the strain energy. All results are compared to test results whenever they are available.

Proefschrift Rijksuniversiteit Groningen. / Met lit.opg. - Met samenvatting in het Nederlands.

Density functional theory is an efficient and useful method of solving single-reference computational chemistry problems, however it struggles with multi-reference systems. Modifications have been developed in order to improve the capabilities of density functional theory. In this work, density functional theory has been successfully applied to solve multi-reference systems with large amounts of non-dynamical correlation by use of modifications. It has also been successfully applied for geometry optimizations for lanthanide trifluorides.

Made available in DSpace on 2016-08-19T12:56:38Z (GMT). No. of bitstreams: 1 dissertacao Hawbertt.pdf: 1784434 bytes, checksum: a91c14bbd01d8e403347116b6955398d (MD5) Previous issue date: 2012-01-31 / FUNDAÇÃO DE AMPARO À PESQUISA E AO DESENVOLVIMENTO CIENTIFICO E TECNOLÓGICO DO MARANHÃO / This work presents computational studies of complexes of Fe (II) TAA and Mn (II) TAA using calculations based on density functional theory (DFT). Thus, Fe (II) TAA and Mn (II) TAA, with various multiplicities, were optimized and a comparative study with experimental data was conducted to investigate the distances and bond angles as well as other parameters such as the total energy and the frontier orbitals (HOMO-LUMO). In addition, we also carried out calculations of these complexes with molecular oxygen adsorbed in order to analyze the catalytic behavior for the oxygen reduction reaction. Thus, the lower binding energy and vibrational frequencies of the complex of Fe (II) TAA gave it a higher catalytic activity for this purpose. / Este trabalho apresenta estudos computacionais dos complexos de Fe(II)TAA e Mn(II)TAA usando cálculos com base na teoria funcional da densidade (DFT). Sendo assim, Fe(II)TAA e Mn(II)TAA, com várias multiplicidades, foram otimizadas e um estudo comparativo com dados experimentais foi realizado, a fim de investigar as distâncias e ângulos de ligação, bem como outros parâmetros, como, a energia total e os orbitais de fronteira (HOMO-LUMO). Além disso, também foram realizados cálculos destes complexos com oxigênio molecular adsorvido, a fim de se analisar o comportamento catalítico para a reação de redução de oxigênio. Desse modo, a menor energia de ligação e frequências vibracionais do complexo de Fe(II)TAA lhe conferiu uma maior atividade catalítica para este propósito.

<p>Utilizing a genetic algorithm training of the atom dipole interaction model was performed to arrive at C,H, N, & O atomic polarizabilities that constitute a correction to semiempirical molecular polarizability calculations increasing the accuracy of these calculations to near parity with DFT at a fraction of the computational load.</p>

Объект исследования – наноразмерные пленки двумерно упорядоченного линейно - цепочечного углерода на металлической подложке без примесей и с примесями. Цель работы – теоретическое исследование структурных, механических и колебательных свойств наноразмерных пленок двумерно упорядоченного линейно - цепочечного углерода на металлической подложке. Методы исследования: метода функционала плотности (DFT), сделан обзор экспериментальных и теоретических работ по применению DFT для вычисления структурных, упругих и колебательных свойств; использование пакетов ABINIT и Quantum-Espresso в приближении DFT; графическое представление результатов с помощью программного обеспечения MS Office Excel и Origin Pro. Результаты работы: рассчитан спектр комбинационного рассеяние ЛЦУ пленок; совмещение экспериментального и расчетного спектров комбинационного рассеяния для линейной структурной модели кристалла карбина; анализ возможности аттестации линейно-цепочечных структур методом КРС. / The object of investigation is nanosized films of two-dimensionally ordered linear-chained carbon on a metal substrate without impurities and with impurities. The aim of the work is a theoretical study of structural, mechanical and vibrational properties of nanosized films of two - dimensional ordered linear - chain carbon on a metallic substrate. Research methods: density functional method (DFT), an overview of experimental and theoretical works on DFT application for calculation of structural, elastic and vibrational properties; the use of Abinit and Quantum-Espresso packages in the DFT approximation; graphical representation of results. The results of the work: the spectrum of Raman scattering of LCC films was calculated; combining the experimental and calculated Raman spectra for the linear structural model of a carbyne crystal, analysis of the possibility of characterization of linear-chained structures by the Raman spectroscopy method was performed.