A carregar...
Publicação
Ab-initio design of bulk materials assembled with silicon clusters
| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 29.12 MB | Adobe PDF |
Autores
Orientador(es)
Resumo(s)
The fact that the founding papers of Density Functional Theory are among the most
cited papers ever, testi es for the importance of Quantum Mechanics and its (often)
counter intuitive features in characterizing many-particle systems at a nano and
sub-nano scale. Density Functional Theory has enabled one to use the computer to
predict quantitatively several of the properties of the aforementioned many-particle
systems. The prediction of new materials, often exhibiting meta-stability, is one of
its distinctive features. In this work we will discuss a new class of meta-materials
which, being silicon based, exhibit properties which in no way resemble those of its
main constituent. We investigate the feasibility of assembling the exceptionally stable
isovalent X@Si16 (X=Ti, Zr and Hf) nanoparticles to form new bulk materials.
We use rst principles density functional theory. Our results predict the formation
of stable, wide band-gap materials crystallizing in HCP structures in which the cages
bind weakly, similar to fullerite. The present study suggests new pathways through
which endohedral cage clusters may constitute viable means toward the production
of synthetic materials with pre-de ned physical and chemical properties. Within
the same rst-principles framework we will investigate the vibrational modes and
infrared spectra of the isovalent X@Si16 (X=Ti, Zr and Hf) nanoparticles. Our results
predict the existence of high-intensity modes of low frequency. An estimate of
the electron-phonon coupling strength is also provided based on a single-molecule
method introduced recently. The large value of combined with predicted stability
of bulk materials assembled with these nanoparticles suggest that these new materials,
when appropriately doped, may exhibit high-temperature superconducting
properties.
Descrição
Tese de doutoramento, Física, Universidade de Lisboa, Faculdade de Ciências, 2011
Palavras-chave
Nanofísica Materiais nanoestruturados Clusters de silício Supercondutividade Teses de doutoramento - 2011