Dissertation > Excellent graduate degree dissertation topics show

The Evolution of Geometric and Electronic Structures of Small [Ti_n-mH₂]^x（n=2～7, m=1～21, x=-1, 0, 1） Clusters

Author: ShangMingHui
Tutor: ZhuYueJin；WeiShiHao
School: Ningbo University
Course: Theoretical Physics
Keywords: Clusters Generalized gradient approximation (GGA) Density functional theory (DFT) Average number of Millikan charge (AMC) The Millikan occupation (AMO)
CLC: O469
Type: Master's thesis
Year: 2009
Downloads: 11
Quote: 0
Read: Download Dissertation

Abstract

Under the density functional theory (DFT) based generalized gradient approximation (GGA), a systematic study of a small system titanium metal clusters (the Ti _n-mH ₂ n = 2 ~ 7, m = 1 ~ 22) adsorption the stable geometry after a different number of hydrogen molecules and its corresponding electronic structure. Found that: (1) When the titanium metal clusters (Ti _n) only adsorption of a hydrogen molecule: N LT; the HH bond between the hydrogen molecules being interrupted respectively adsorbed in two adjacent ribs; when n = 5 is a rib - a turning point in the adsorption of a hydrogen molecule: the hydrogen molecules in the adsorption on the surface, while the other one hydrogen atom is still adsorbed to the edge on; When N GT; 5 pm, The two hydrogen atoms are located in two adjacent surface; (2) we get a different titanium the Clusters (Ti _n, n = 2 to 7) adsorption of hydrogen molecules, saturated structure and found that Ti2 and Ti3 per Ti atom average chemical adsorption of up to 5-number object of hydrogen molecules; decreases with the increase of the number of titanium clusters, the number of hydrogen molecules are adsorbed by each of the Ti atom, but for Ti7, still reach 3 and others have pointed out the \P. Tarakeshw-ar et al noted 15 hydrogen molecules. (3) When the adsorption of a different number of the number of hydrogen molecules (m) of Ti metal clusters Ti7 found that: when the number m of the adsorbed hydrogen molecules when hydrogen molecules are decomposed into hydrogen atoms in the form of the adsorbed on Ti7 on; about about m = 10, start at the same time a hydrogen molecule, a hydrogen atom adsorbed on the Ti7 on; when m ≤ 19, Ti7 clusters are kept pentagonal pyramid structure (D5H), and when m ≥ 21, Ti7 Clusters mutations, the structure of the class C3v structure; (4) from the Ti _n-mH ₂ of the electronic structure of clusters analysis, we find that: As the adsorption of the increase of the number m of the hydrogen molecules, clusters occurs between the atomic orbital in a more complex orbit hybrid interactions, in addition to the Ti atom of valence electron 3d, 4s, inner electron 3s, 3p, and non-occupied orbital 4p also involved in the orbital hybridization interaction; from PDOS figure can also be seen, TI the 3d state density as the adsorption of the increase of the number of hydrogen molecules from the vicinity of the Fermi level broadening to a deep level; through the Millikan occupation analysis, we learned that: Ti atoms in electronics, in particular, on the 3d orbitals electron transfer to H 1s orbital, leading to greatly enhanced Coulomb interaction in the hydrogen molecule, thereby interrupting the HH bond, making the hydrogen molecule dissociative adsorption to Ti _n clusters. In addition, we studied the small system Ti _n-MH _²] x (n = 2 to 7; m = 0 to 22; x = -1, 1) clusters. By analyzing the number of each atom, Millikan occupied (Atomic Mulliken Occupation, AMO), found that the When Ti _n-mH ₂ Clusters charged, the charge of the clusters will reallocate . Ti _n-mH ₂ Ti-Ti and Ti-H chemical bonds in the cluster because of the re-allocation of the charge changed significantly. In addition to the the 'Ti ₆-18H ₂-G _n' and 'the Ti ₇-21H _{2 < / sub>-G _p 'two clusters effective volume did not change significantly, the charged cluster structure with respect to the neutral structures looser, and clusters of geometric structure a certain degree of distortion. Found through research the clusters of Ti _n-mh ₂ having a larger ionization energy and electron affinity, and to be able to show that these clusters have a strong chemical stability.}

The Evolution of Geometric and Electronic Structures of Small [Tin-mH2]x（n=2～7, m=1～21, x=-1, 0, 1） Clusters

Abstract

Related Dissertations

The Evolution of Geometric and Electronic Structures of Small [Ti_n-mH₂]^x（n=2～7, m=1～21, x=-1, 0, 1） Clusters