Electronic polarization, Physics

It is defined as an electric strain produced in an atom due to application of external electric field to the bulk material. It is the result of the displacement of the positively charged nucleus and the negative electron of an atom in opposite direction. It is also called atom or atomic polarization. The paradigmatic material for the simple case of atoms with a spherical symmetry is the noble gases in all aggregate forms. For computing the effect of electronic polarization, we take an idealized atom with "Perfect spherical symmetry".

(A)It has a point like charge +Zee in the nucleus, and

(B)The exact opposite charge -Zee homogenously distributed in the volume of the atom, which is

          V=    4π R/3

(c)The volume charge density of the electron is ρ=-3Ze/4πr3

 (D)In an electrical field E a force F1 acts on charges given by

              F 1 =Z.e.E

(E)The positive charge in the nucleus and the centre of the negative charges from the electron "cloud" will thus experience forces in different direction and will become separated. We have idealized situation show.

(F)The separation distanced will have a finite value because the separating force of the external field is exactly balanced by the attractive force between the centres of charges at the distance d. The attractive force F 2 thus is given by

             F2=q (Nucleus).q (e in d)/4πεod2

(G) With q (Nucleus) =Zee and q (e in d=the fraction of the charge of the electrons contained in the sphere with the radios d, which is just the relation of the total volume of the sphere with radios d. Now we calculate the induced dipole moment, which is



The polarization P finally is given by multiplying with N, the density of the dipoles, we obtain


(H) This is our first basic result concerning the polarization of a material and its resulting susceptibility. There are various interesting points:

We justified the law of a linear relationship between E and P for the number of electronic polarization mechanisms. We can simply extend the result to a mix of different atoms. All we need to do is to sum over the relative densities of every type of atom. Concluding that electronic polarization is completely unimportant would be premature, however. Atoms in crystals or in any e a solids do not generally have spherical symmetry. Consider the Sp3 orbital of Si, Gee or diamond. Without a field, the centre of the negative charge of the electron orbital's will still coincide with the core but an external field breaks that symmetry producing a dipole momentum. The effect can be large compared to spherical S-orbital's: Si has a dielectric constant of 21, which comes exclusively from electronic polarization.

Posted Date: 7/7/2012 4:26:58 AM | Location : United States

Related Discussions:- Electronic polarization, Assignment Help, Ask Question on Electronic polarization, Get Answer, Expert's Help, Electronic polarization Discussions

Write discussion on Electronic polarization
Your posts are moderated
Related Questions
Q What is temperature of inversion? Maintain the temperature of the cold junction constant the temperature of the hot junction is gradually increased. The thermo emf increase

Q. Give any three applications of the superconductors. i) High efficiency ore-separating machines may be built using superconducting magnets which can be used to separate tumou

as flux = E.A and flux density is equal to flux/A then why A/A cannot e cancelled ?

a body travelling with uniform acceleration crosses two points A &B with velocities 30m/s & 50m/s the speed of the body at mid point of A&B is approximately?

Q. State Brewster's law. Brewster's law the digression of the polarising angle is numerically equal to the refractive index of the medium. That is tan ip = μ

The Venturimeter (see figure) is a device used to calculate the flow speed of a fluid in a pipe. At the throat, the area is decreased from A to a and the velocity is increased from

Q. State the law of conservation of electric charges? The entirety charge in an isolated system always remains constant. For instance Uranium ( 92 U 238 ) can decay by emittin

show that work is a path function not a property

A rectangular surface (0.14 m x 0.39 m) is oriented in a uniform electric field of 440 N/C. What is the maximum possible electric flux through the surface?

For the circuit shown in Figure , verify the value of V1. If the total circuit resistance is 36Ω. Determine the supply current and the value of resistors R 1 , R 2 and R 3