Effect of hydrogen on ground state structures of small silicon clusters

We present results for ground state structures of small Si$_{n}$H (2 \leq \emph{n} \leq 10) clusters using the Car-Parrinello molecular dynamics. In particular, we focus on how the addition of a hydrogen atom affects the ground state geometry, total energy and the first excited electronic level gap of an Si$_{n}$ cluster. We discuss the nature of bonding of hydrogen in these clusters. We find that hydrogen bonds with two silicon atoms only in Si$_{2}$H, Si$_{3}$H and Si$_{5}$H clusters, while in other clusters (i.e. Si$_{4}$H, Si$_{6}$H, Si$_{7}$H, Si$_{8}$H, Si$_{9}$H and Si$_{10}$H) hydrogen is bonded to only one silicon atom. Also in the case of a compact and closed silicon cluster hydrogen bonds to the cluster from outside. We find that the first excited electronic level gap of Si$_{n}$ and Si$_{n}$H fluctuates as a function of size and this may provide a first principles basis for the short-range potential fluctuations in hydrogenated amorphous silicon. Our results show that the addition of a single hydrogen can cause large changes in the electronic structure of a silicon cluster, though the geometry is not much affected. Our calculation of the lowest energy fragmentation products of Si$_{n}$H clusters shows that hydrogen is easily removed from Si$_{n}$H clusters.Comment: one latex file named script.tex including table and figure caption. Six postscript figure files. figure_1a.ps and figure_1b.ps are files representing Fig. 1 in the main tex

Carta topografica della provincia di Roma e regioni limitrofe fino ad Avezzano; Spoleto e Gaeta; con cartina speciale dei Colli Albani

1 Mapa, color. - Secondo i recenti rilievi del R. Stato Maggiore con speciali indicazioni dell'altimetria, delle reti stradali e delle circoscrizioni amministrative ed elettorali. - Finestra: I Colli Albani, 1:75 000 (25 x 27 cm)1:250 00075 x 72 cm; full 87 x 76 c

On the Relationship among Learning Style, Perceived, Learning and Performance in an Experiential Learning Environment

"This investigation was undertaken in order to discover whether there is a significant relationship between a student’s learning style, his perception of knowledge acquisition, and his course performance. The following three hypotheses were developed to provide focus for the study: 1. Specific learning styles are associated with high student performance, while other styles are associated with lower performance. 2. Certain learning styles are associated with a perception of a great deal of learning while other styles are associated with a perception of little learning. 3. Students’ perception of learning is directly related to students’ measured learning. The data for this study is being gathered from students in four sections of marketing principles at the Rochester Institute Technology during the Fall quarter, 1975. Learning style data is being gathered using instruments designed by Kolb, Gasha, and Smith. Perceived learning data will be collected using an instrument designed by the author. The performance measure will be represented by the individual student’s weighted average for the course. This includes two examinations, game performance, and class participation. These data will then be analyzed using the appropriate statistical techniques to test the hypotheses. The analysis will be based upon the individual student not a team. The performance measure, as stated above, is the student’s course average. The author believes, with some support from the literature, that game performance is not necessarily the same as knowledge gained from playing a simulation. It is believed that the course average, which includes several types of learning measures, is much superior to game performance as a measure of learning.

Carta topografica della provincia di Roma e regioni limitrofe fino ad Avezzano; Spoleto e Gaeta; con cartina speciale dei Colli Albani

1 Mapa, color. - Secondo i recenti rilievi del R. Stato Maggiore con speciali indicazioni dell'altimetria, delle reti stradali e delle circoscrizioni amministrative ed elettorali. - Finestra: I Colli Albani, 1:75 000 (25 x 27 cm)1:250 00075 x 72 cm; full 87 x 76 c