Universidade de Lisboa Repositório da Universidade de Lisboa

Repositório da Universidade de Lisboa >
Faculdade de Ciências (FC) >
FC - Teses de Doutoramento >

Please use this identifier to cite or link to this item: http://hdl.handle.net/10451/1676

Título: Understanding electronic properties of water: a theoretical approach to the calculation of the adiabatic band gap of liquid water
Autor: Couto, Paulo Cabral do, 1967-
Orientador: Cabral, Benedito José Costa, 1951-
Simões, José Artur de Sousa Martinho, 1952-
Palavras-chave: Química física
Teses de doutoramento
Issue Date: 2007
Resumo: Electronic properties of condensed phase water are not very well understood. They are, however, of fundamental importance for a molecular level understanding of the properties of water as well as the role of water, both as participant and medium where chemical reactions occur. It is generally accepted that bulk water can be described as a lone pair amorphous insulator or a large gap lone-pair amorphous semiconductor and the condensed phase ionization potential de_ned as a vertical quantity. A usually accepted value is 8.7 _ 0.5 eV. However, a de_nition of condensed phase properties such as the condensed phase ionization potential is not straightforward and ultimately dependent our understanding of the elementary mechanisms for ionization/excitation in condensed phase water. A longstanding issue is the concearns the fact that hydrated electrons are produced by photoabsorption at _6.5 eV. It has recently been pointed out that the ability of water to reorganize about charged (and neutral) molecules, as well as the reactive nature of electronically excited water molecules, should be taken into account in explaining observed aqueous anion thermochemical and photochemical properties. Moreover, it has been shown that an adiabatic route for accessing the conduction band of liquid water can be de_ned and that the bottom of the conduction band is characterized by the reorganization of the water molecules around the H3O+ cation and OH radical as well as by the presence of a delocalized or quasi-free electron. A _6.9 eV value was proposed by J.V. Coe [Int. Rev. Phys. Chem. 20, 33, 2001], based on known aqueous anion thermochemical and photochemical properties,The present work presents a theoretical estimate for two key reference quantities required for the quantitative estimate of the adiabatic band gap of pure liquidwater as de_ned by J.V. Coe: the hydration energy of the hydroxyl radical andthe electron a_nity of liquid water. The hydration of the hydroxyl radical wasinvestigated by microsolvation modeling and statistical mechanics Monte Carlosimulation. The electron electronic density of states and a_nity of liquid water wasinvestigated trough a sequential Quantum Mechanical / Monte Carlo methodology.Finally, as the adiabatic approach for a de_nition of a band gap for pure liquidwater is based on macroscopic quantities, a molecular level veri_cation of the adiabatic picture was also undertaken.
Descrição: Tese de doutoramento em Química (Química-Física), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008
URI: http://hdl.handle.net/10451/1676
Appears in Collections:FC - Teses de Doutoramento

Files in This Item:

File Description SizeFormat
3653_TESE.pdf5,4 MBAdobe PDFView/Open
Statistics
FacebookTwitterDeliciousLinkedInDiggGoogle BookmarksMySpaceOrkut
Formato BibTex mendeley Endnote Logotipo do DeGóis 

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

 

  © Universidade de Lisboa / SIBUL
Alameda da Universidade | Cidade Universitária | 1649-004 Lisboa | Portugal
Tel. +351 217967624 | Fax +351 217933624 | repositorio@reitoria.ul.pt - Feedback - Statistics
DeGóis
Promotores do RCAAP   Financiadores do RCAAP

Fundação para a Ciência e a Tecnologia Universidade do Minho   Governo Português Ministério da Educação e Ciência PO Sociedade do Conhecimento (POSC) Portal oficial da União Europeia