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

                                                                      Induced=qd=Ze.de=4πε0R3E

                              P=4πε0R3E

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

                               P=4πε0R3NE

(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
what do you mean by retardation plates?explain their functioning by taking an example of a quarter wave plate

Question: The external surface of a short vertical segment of plastic pipe is hidden from view by wire wrapped around the pipe. Current flows clockwise as out looked from above

The ordered arrangements of radiations according to wavelengths or frequencies are called as Spectrum. Spectrum may be divide in two parts Emission spectrum and Absorption spectrum

The plane of polarization of a plane polarized light is rotated through an angle of 200 while passing through 20 cm in a sugar solution having rotation about 45 0 cm 2 /gm. Determ

With the help of relevant diagrams, define the following terms: (i) Pulse-position modulation (PPM) (i) Pulse-duration modulation (PPM)

(i)  X-rays are electromagnetic waves with wavelength lie among 0.1Å - 100Å. (ii)  X-rays is invisible. (iii) They always go in a straight line with speed of light. (iv) X

Thermodynamic laws: First law of thermodynamics In internal energy of a system the change is the total heat transferred to or from the system & the work done on or by

if two metal spheres are mounted on insulators then how will we give them equal charge by using a charged glass rod?

A Neutron Star is formed in the aftermath of a Supernova explosion. The star was originally rotating with a period of 20 days and had a mass of 2x10 30 kg and radius of 6x10 8 m.

Internal Resistance of Circuit: As mentioned earlier in the section on batteries, every source of electricity, such as a cell or generator has resistance to current flow called