Ab-initio study the electronic structure of InXGa1-XP nanocrystals

العناوين الأخرى

دراسة التركيب الإلكتروني لبلورات الانديوم كاليوم فوسفايد النانوية باستعمال صياغة المبادئ الأساسية

مقدم أطروحة جامعية

Abd al-Rahim, Dhikri Qasim

مشرف أطروحة جامعية

Husayn, Muhammad Taqi

الجامعة

جامعة بغداد

الكلية

كلية العلوم

القسم الأكاديمي

قسم الفيزياء

دولة الجامعة

العراق

الدرجة العلمية

دكتوراه

تاريخ الدرجة العلمية

2013

الملخص الإنجليزي

Ab- initio Density functional theory (Ab-initio-DFT) at the generalized-gradient approximation (GGA) level with STO-3G basis set coupled with large unit cell method is used in the present work to determine the electronic structure for InXGa1-XP nanocrystals.

Nanocrystals structure is divided into two parts core and surface.

The core part for sizes (8, 16, 54, 64 and 128) and concentration for (x=0, 0.25, 0.5, 0.75 and 1) calculation with 3D periodic boundary condition (PBC), while the surface part include only (8 atoms) for concentration (x=0, 1)with 2D PBC calculation were used to simulate oxygenated (001)-(1x1) surface.

Two kinds of cells are investigated; Bravais cubic cell multiples and primitive parallelepiped cell multiples.

Gaussain 03 programs are prepared to perform computations using Fortran as a programming language.

Position and properties of atoms which compose these crystals are entered as input data.

The final modified LUC-DFT equations are embodied in these computer routines and solved by iterative methods (self consistent field method (SCF)).

Results show that shape effects are strong compared with other previously investigated semiconductor elements and compounds which are attributed to different atomic electronic properties.

Many properties fluctuate indefinitely while other properties converge to definite values.

Abstract XIV Quantities such as ionicity, cohesive energy and density of states reach definite values.

However, energy gap, conduction band, electron affinity ionization potential fluctuates indefinitely depending on the shape and surfaces of the nanocrystal.

Results for zinc blende III-V InP and GaP core part for (8 atoms) show the value of energy gap are equal to (1.29 , 1.64)eV respectively, while the energy gap for InP-O and GaP-O at the same core part are equal to (0.33, 0.21)eV respectively.

The lattice constant for InP-O and GaP-O was about (0.53, 0.513)nm respectively, which slightly smaller than for the core part is equal to (0.57, 0.52)nm respectively.

The valence and conduction bands width is wider and lower density of states to the surface part compare with the core part for InP and GaP.

The energy gap for alloying composition InXGa1-XP is equal to (1.41 eV) its between that for InP and GaP when x=0.5, while when x=0.75 and 0.25 the energy gap around to ~1eV.

However, energy gap, conduction band, highest occupied orbital, lowest unoccupied orbital fluctuates indefinitely depending on the shape of the nanocrystal.

While the total energy and cohesive energy are proportional linear with the number of core for all concentration .

التخصصات الرئيسية

الفيزياء

عدد الصفحات

178

قائمة المحتويات

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-608097