1. 学习网：wu.wuxing.xing5@gmail.com ;
Physics properties of material 1. Dielectric properties 2. Magnetic properties Long Yi ;
密码：wuxing2010

4. 学习方法：
1。作业（40分）：
每人做一次作业。但是每人作业不同：
作业1。将其中一节译成中文，或者校正其中一节，便于同学学习。
要求：在规定的时间以前传上网，上课用。
专用名词翻译准确，文字通顺。
公式要写出来。
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步骤清楚。
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每人的作业在网上 。

5. 2。考试(60分）：
开卷，6道题，2.5小时，不设考场和监考，成绩和交卷时间相关。
考题和习题相似。
3。分数可以考虑整体提高。
去年：60-80：35，80-90：40，90-100：28

6. 7.1
1。相对介电常数定义:
The relative permittivity( dielectric constant) r is defined to reflect a increase in the capacitance:
意义:
The increase in the stored charge is due to the polarization of the dielectric by the applied field.

7. 2。The definition of electric dipole moment.
意义:

8. 3。Definition of Polarizability
pinduced = E
pinduced = induced dipole moment,  = polarizability, E = electric field
极化率,

9. Electronic Polarization举例
Electronic Polarization
pe = magnitude of the induced electronic dipole moment, Z = number of electrons orbiting the nucleus of the atom, x = distance between the nucleus and the center of negative charge,  = constant, E = electric field

10. Static Electronic Polarizability
注意ω的来源
e = electronic polarizability
Z = total number of electrons around the nucleus
me = mass of the electron in free space
o = natural oscillation frequency

11. Examaple 1.7

12. Electronic polarizability and its resonance frequency versus the number of electrons in the
atom (Z). The dashed line is the best-fit line.
注意：f0在光频

13. (a) When a dilectric is placed in an electric field, bound polarization charges appear on the opposite surfaces.
(b) The origin of these polarization charges is the polarization of the molecules of the medium.
(c) We can represent the whole dielectric in terms of its surface polarization charges +QP and -QP.
4.材料的表面极化电荷密度和极化强度定义

14. Definition of Polarization Vector
P = Polarization vector, p1, p2, ..., pN are the dipole moments induced at N molecules in the volume
Definition of Polarization Vector
P = Npav
pav = the average dipole moment per molecule
P = polarization vector, N = number of molecules per unit volume

15. Polarization and Bound Surface Charge Density
P = p
P = polarization, p = polarization charge density on the surface

16. Polarization charge density on the surface of a polarized medium is related to the normal
component of the polarization vector.

17. 5。Definition of Electronic Susceptibility
P = eoE
P = polarization, e = electric susceptibility, o = permittivity of free space, E = electric field

18. Electric Susceptibility and Polarization
e = electric susceptibility, o = permittivity of free space, N = number of molecules per unit volume, e = electronic polarizability
Relative Permittivity and Electronic Susceptibility
r = 1 + e
r = relative permittivity, e = electric susceptibility

19. Relative Permittivity and Polarizability
r = relative permittivity
N = number of molecules per unit volume
e = electronic polarizability
o = permittivity of free space
Assumption: Only electronic polarization is present

20. The electric field inside a polarized dielectric at the atomic scale is not uniform.
The local field is the actual field that acts on a molecules.
It can be calculated by removing that molecules and evaluating the field at that point from the charges on the plates and the dipoles surrounding the point.

21. Local Field in Dielectrics
Eloc = local field, E = electric field, o = permittivity of free space, P = polarization
Clausius-Mossotti Equation
r = relative permittivity, N = number of molecules per unit volume, e = electronic polarizability, o = permittivity of free space

22. Example 7.2

23. 6.共价键晶体中电子极化
(a) Valence electrons in covalent bonds in the absence of an applied field.
(b) When an electric field is applied to a covalent solid, the valence electrons in the covalent bonds are shifted very easily with respect to the positive ionic cores. The whole solid becomes polarized due to the collective shift in the negative charge distribution of the valence electrons.

26. 7.3 polarization mechanisms
7.3.1离子极化
A NaCl chain in the NaCl crystal without an applied field. Average or net dipole moment per ion is zero.
In the presence of an applied field the ions become slightly displaced which leads to a net average dipole moment per ion.

27. Pav＝αEloc
Ionic Electric Orinetational Polarization

28. 7.3.2。偶极子极化 (a) A HCl molecule possesses a permanent dipole moment p0.
(b) In the absence of a field, thermal agitation of the molecules results in zero net average
dipole moment per molecule.
(c) A dipole such as HCl placed in a field experiences a torque that tries to rotate it to align p0
with the field E.
(d) In the presence of an applied field, the dipoles try to rotate to align with the field against
thermal agitation. There is now a net average dipole moment per molecule along the field.

29. Average Dipole Moment in Orientational Polarization
pav = average dipole moment, po = permanent dipole moment, E = electric field, k = Boltzmann constant, T = temperature
Dipolar Orientational Polarizability
d = dipolar orientational polarizability, po = permanent dipole moment

30. 7.3.3。界面极化
(a) A crystal with equal number of mobile positive ions and fixed negative ions. In the
absence of a field, there is no net separation between all the positive charges and all the
negative charges.
(b) In the presence of an applied field, the mobile positive ions migrate toward the negative
charges and positive charges in the dielectric. The dielectric therefore exhibits interfacial
polarization.
(c) Grain boundaries and interfaces between different materials frequently give rise to
Interfacial polarization.

31. 7.3.4Total Induced Dipole Moment
pav = e Eloc + i Eloc + d Eloc
pav = average dipole moment, Eloc = local electric field, e = electronic polarizability, i = ionic polarizability, d = dipolar (orientational) polarizability
Clausius-Mossotti Equation
r = dielectric constant, o = permittivity of free space, Ne = number of atoms or ions per unit volume, e = electronic polarizability, Ni = number of ion pairs per unit volume , i = ionic polarizability