Ab – initio restricted Hartree - Fock method within the framework of large unit cell (LUC) formalism is used to investigate the electronic structure of Si and Ge nanocrystals. The surface and core properties are investigated. A large unit cell of 8 atoms is used in the present analysis. Cohesive energy, energy gap, conduction and valence band widths are obtained from the electronic structure calculations. The results are compared with available experimental data and theoretical results of other investigators. The calculated lattice constant is found to be slightly larger than the corresponding experimental value because we use only 8 atoms and we compared the results with that of the bulk crystals, nanoclusters are expected to have stronger directional bonds that in their bulk structure. The surface states are found to be mostly non-degenerated because of the effect of surface discontinuity and the existence of oxygen atoms. Valence and conduction bands are found to be wider on the surface due to the splitting of energy levels due to the existence of oxygen atoms. The present method can be used to investigate the electronic structure of bulk, surface and nanocrystals.
Abstract:
Witness the current business environment changes rapidly reflected on the performance of the facility wishing to stay , which is no longer style reaction enough to handle installations with their environment , and quickly began to lose its luster with the emergence of a message and the vision of contemporary business environment from a set of parts interacting with each other and the concept of behavioral includes all dimensions of performance, it is imperative to adopt a system installations influence variables and positive interaction through the development of strategic plans and the use of implementation and follow-up strategies to ensure the effectiveness of the method for meas
... Show More
Is the efficiency of physical and your endurance is of great importance for some activities and field, as it whenever the situation has improved student career was able to perform physical exertion more with energy saving efforts, so the identification of physical aptitude and endurance private students, was based on that there are positively correlated the carrying of training and pregnancy fact on the shoulders of the student. In other words, physical aptitude and endurance in your control level that can be shown by the student during the performance of training and competitions. Therefore, lies the importance of research to test physical aptitude and endurance your help to reveal the career of the body in the light of their relationship
... Show More
The present study aimed at identifying the role of supervisory and training practices in the field education program in achieving course objectives from the perspective of the student teachers in the Faculty of Science and Arts in sharourah, and its relationship to some variables (gender, specialization,estimation). To achieve this, the researcher used the descriptive-analytical method, and the study tool was designed, which consists of (24) items distributed on two axes: the objectives of field education and supervisory and training practices.Then, the study tool was applied to the research sample represented in the entire study community, which consists of (65) male and female students in the Faculty of Sciences and Arts in
... Show MoreWhereas conventional methods of teaching history do not meet the sometimes purpose has suggested some educators strategies modern help to improve the level of students in the education process through activating prior knowledge and employed in positions of current learning, and focus attention on the points and the outstanding elements of the content and practice techniques Calendar criticof ideas and meanings and mental and linguistic activities used to verify the extent of reaching understanding. &n
... Show MoreAbstract
This research aims to determine the role of the quality of higher education in achieving organizational excellence at the universities of Baghdad and Al-Nahren, was based on research on the main hypothesis is:First:- There is correlation and between the quality of higher education dimensions (continuous improvement, measurement and analysis, the culture of the organization, optimal use of resources , customer satisfaction) and organizational excellence dimensions (strategic planning, focusing on the market and the customer, information and analysis, the effectiveness of operations, processes and resources), Second:- Second, there is the impact of relationship sig
... Show More
(1)
The objective of this study is to attempt to provide a quantitative analysis to the causes of unemployment in Iraq and its mechanisms of generation, as well as a review of the most important types of both visible and invisible unemployment, and an attempt to measure the disguised unemployment and analyze the causes. The problem of the research lies in the fact that the Iraqi Economy has been suffered for a long time although its characterized by abundant physical and natural resources, from the existence of the phenomenon of unemployment in the previous two types. Causing a lot of economic problems, represented by the great waste of resources and
... Show More