Ph6251 phy2 notes, engineering physics 2 lecture notes. We can produce an improved model by solving schrodingers equation for the periodic potential shown in figure \\pageindex1\. Free electrons in the conduction band are coupled to the electric field of the optical wave, become accelerated and. The theory has been developed in three main stages. Thompson and hendrik lorentz and mind you, lorentz and zeeman determined the emratio before thompson. Then sommerfelds elementary quantum mechanical theory of metals is discussed.
Quantum free electron theory is a microscopic theory developed by sommerfeld. Free electron theory of solids mini physics learn physics. Ppt on free electron theory electrical resistivity and. The question that caused the greatest difficulty in the early development of the electron theory of metals concerns the heat capacity of the conduction electrons. According to this theory, the metals containing free electrons obey the laws of classical mechanics. Optical properties of solids department of physics. It was developed in 1927, principally by arnold sommerfeld, who combined the classical drude model with quantum mechanical fermidirac statistics and hence it is also known as the drudesommerfeld model. Bloch theorem and band structure, nearly free electron approximation. In a solid, the valence electrons interact and form a gas of electrons. The development of the quantummechanical electron theory of metals. Thermal properties of the free electron gas the fermidirac distribution derivation the n electron state is speci ed by a list of the one electron levels occupied states k. These valence electrons are weakly bound with the atoms. Classical free electron theory drudelorentz theory. Well examine the assumption of a constant potential.
Quantum theory of solids is a modern presentation of theoretical solid state physics it builds directly on the same author. In the classical theory of free electron model, it is taken as the average distance travelled by the conduction electrons between successive collisions with the. Engineering physics pdf notes free download 2020 sw. Introduction to solid state physics spring 2016 helmut schiessel 1 the drude theory of metals 1.
The free electron model drude, 1900 provides an excellent account for the absorption by metallic surfaces at relatively low photon energies of the longwavelength range. Electron theory of metals pes college of engineering. See band theory of solids, bloch theorem, fermidirac statistics, statistical mechanics. Bloch theorem, phonons in one dimension, periodicity, effect of a basis on the electronic structure, crystal structures, the reciprocal lattice. The outer most electrons of metal atoms are also known as valence electrons. Srit unit iii free electron theory applied physics. This document is highly rated by electronics and communication engineering ece students and has been viewed 1743 times. An introduction to the electron theory of solids introduces the reader to the electron theory of solids. It is a microscopic theory, proposed by sommerfeld in 1928. Ziman, principles of the theory of solids, cambridge, 1972, chapter 3.
Solid state physics problems and solutions download book. According to the classical free electron theory the value of specific heat of metals is given by 4. Introduction to the basic concepts of the quantum theory of solids. Ueep2024 solid state physics topic 3 free electron in metals 2. Orlando february 9, 2004 the source of the binding energy is primarily the electrostatic potential. One dimensional electron energy bands for the nearly free electron model shown. In freeelectron masers fems two regimes of the electron wave coupling are mainly used, namely, the regime of inertial electron bunching 1. Publication date 1963 topics solid state physics, quantum theory publisher.
The free electron model in solids discussed in the previous section is very useful in order to explain some of the electrical properties of metals. Theories started accelerating after the discovery of the electron by j. The band theory of solids was developed by bloch in 1928. An introduction to the electron theory of solids sciencedirect. The classical theory fails to explain the heat capacity and the.
The current script will give you all the information you need for following this introductory course. Pdf free electron theory 201516 vtu shashank mohan. Solid state theory walter a harrison pdf free shiftfasr. The phenomena such a photoelectric effect, compton effect and the black body radiation couldnt be explained by classical free electron theory. Each ion in the solid is the source of a coulomb potential. Drudes classical theory of electrical conduction drude assumed that a metal is composed of ions, which are stationary, and valence electrons, which are free to move. Harrison 1970 detailed discussion of band structure calculations. Applying perturbation theory to free electron wavefunctions and nearly free electron model. A level chemistry multiple choice questions and answers pdf book to download covers solved quiz questions and answers pdf on topics. According to free electron theory, the properties of a metal depends on gas of free electrons. It explains the binding in solids, behaviour of conductors and insulators, ferromagnetism, electrical and thermal conductivities of solids, elasticity, cohesive and repulsive forces in solids. Classical theory drude model drude model, 1900ad, after thompsons discovery of electrons in 1897 based on the concept of kinetic theory of neutral dilute ideal gas apply to the dense electrons in metals by the free electron gas picture success.
Drude theory of conduction basics of free electron theory and electrical conductivity part. An introduction to the electron theory of solids 1st edition. The goal is not to provide a better description of electrons or atomic cores, but to nd the most fundamental theory of physics. Goswamy associate professor in physics uiet, panjab university, chandigarh. In solids, electrons in outer most orbits of atoms determine its electrical properties.
The classical theory of solids essentially treats a solid as a gas of electrons in the same fashion as boltzmanns theory of gases. According to this theory, the free electrons move in a periodic potential proved by the crystal lattice. Though quantum theory explained several phenomena, it is failed in explaining the classification of solid into metals, semiconductors and insulators therefore. Solid state physics semiclassical motion in a magnetic. Even in the context of a freeelectron gas, there are strong coulomb interactions between electrons which are frequently neglected in the freeelectron theory of metals. According to this theory, the electrons in a metals move in a constant potential. Relaxation time and drift velocity, failures of classical free electron theory, quantum free electron theory, fermidirac distribution, fermi energy, failures of quantum free electron theory. Mar 29, 2015 free electron theory of solids march 29, 2015 december 30, 2010 by mini physics electrons can be visualised as rattling around insde the metal, randomly changing direction when they collide with positive ions, much like a ball in a pinball machine. Free solid state physics books download ebooks online.
Topics covered range from the breakdown of classical theory to atomic spectra and the old quantum theory, as well as the uncertainty principle of heisenberg and the foundations of quantum mechanics. Snokes website there is also a pdf version for download. Freeelectron theory of metals accessscience from mcgrawhill. Free electron theory drudes and lorentz free electron model. College chemistry multiple choice questions and answers mcqs. Especially classical free electron theory and quantum free electron theory of metals. The valence electrons of atoms are free to move about the whole volume of the metal, like the molecules of a perfect gas in a container. Building on this, it develops the theory of electrons in an n atom solid the band concept and its application to electrical and thermal properties in solids. In metals there are large number of free electrons moving freely in all possible directions. Theory of solids i physics mit opencourseware free. The drude model was the rst attempt to use the idea of a \gas of electrons, free to move between positively charged ionic cores.
It explains the binding in solids, behaviour of conductors and insulators, ferromagnetism, electrical and thermal conductivities of solids, elasticity, cohesive and repulsive forces in solids etc. In the nearly free electron approximation, interactions between electrons are completely ignored. Assumptions or salient features in classical free electron theory the classical free electron theory is based on the following postulates. These electrons in the material are then termed quasiparticles. In solid state physics, the free electron model is a simple model for the behaviour of charge carriers in a metallic solid. Atomic selectrons are delocalised due to overlap of outer orbits. Notice that the free electron model is productive because the average of this field is approximately constant.
Free electron model put free electrons into a very wide potential well the same size as the crystal i. Page 2 theory of metals free electron theory of metals band theory of solids dr. In classical free electron theory, proposed by drude and. How to compute the paramagnetism, diamagnetism, or ferromagnetism of solids was not. The electron theory of solids has been developed in three main stages. In metals there are large number of free electrons moving freely in all. The course aims to introduce electronic properties of solids starting from a very simple example. In solid state physics, and these topics themselves will be developed.
Freeelectron theory of metals article about freeelectron. Given its simplicity, it is surprisingly successful in. Applying perturbation theory to free electron wavefunctions and creation of energy gap. Free solid state physics books download ebooks online textbooks. In solid state physics, the free electron model is a simple model for the behaviour of valence electrons in a crystal structure of a metallic solid. Free electron theory of solids march 29, 2015 december 30, 2010 by mini physics electrons can be visualised as rattling around insde the metal, randomly changing direction when they collide with positive ions, much like a ball in a pinball machine. Scattering theory of everything 7 1d scattering pattern 7 pointlike scatterers on a bravais lattice in 3d 7 general case of a bravais lattice with basis 8 example.
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