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
Diamagnetism is a basic property of all matter, though it is generally very weak. It is due to the no cooperative behaviour of oepenrbiting electrons when exposed to an applied mag

Elasticity is defined as the ability of a solid to return to its original shape even after being expanded or contracted. Elasticity is termed as the property of a solid to return t

A simple jack screw Bore a hole by a block of wood to fit a carriage bolt. Choose a bolt that is threaded nearly its whole length. Sink the head of the bolt in the wood, so tha

a column of water contains fine metal particles of radius 2*E(-8) m, which are in thermal equillibrium at 298 K. if there are 1000 particles per unit volume at a given height,how m

if you drop a ball from a tall building, after 4.2 seconds what is its speed in m/s?

Q State Joule's law of heating? The heat produced in a conductor is (i) Unswervingly proportional to the square of the current for a given R (ii) Unswervingly proportiona

What is a capacitor ? A capacitor is basically a two conductors conencted with an insulator.... It stores great amount of charge!

A mirror cleaned with an alcohol solution is slightly colder right after it is cleaned. Why?

Clock spring balance A sensitive balance for use among 0-1 g or 1-10 g is readily made using a piece of clock spring and a block of wood or cotton reel.  Fasten the wooden b

Excitation of Modes in Fiber A multimode fiber is used to couple light into a single mode fiber. Both fibers have the same total diameter. Explain the coupling. Use