Potential energy of quadrupole moments

In summary, the equation that is needed to calculate the potential energy of 2 quadrupole moments and their mutual distance is difficult to find and requires 4 different indices.
  • #1
Gavroy
235
0
hi

i am looking for an equation that gives me the potential energy of 2 quadrupole moments and their mutual distance is assumed to be large.

and they have no total charge or dipole moments.

does such an equation exist?
 
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  • #2
Are you sure you want to see this? It's rather complicated. Let's write down the dipole-dipole interaction first. An electric dipole moment is described by a vector p. The electrostatic potential energy between two dipoles p and p' a distance r apart is

W = (p.p' -3 (n.p)(n.p'))/r3

where n is the unit vector pointing from one dipole to the other.

Ok similarly, the quadrupole moment of an object is described by a symmetric traceless tensor Q. The electrostatic potential energy between two quadrupoles Q and Q' is given by

W = (Q:Q' -10 n.Q.Q'.n + 35/3 (n.Q.n)(n.Q'.n))/r5

Maybe you'd rather see this written out explicitly with all the indices.

Φ = (QijQ'ij - 10 niQijQ'jknk + 35/3 niQijnj nkQ'klnl)/r5
 
  • #3
Bill_K said:
Are you sure you want to see this? It's rather complicated. Let's write down the dipole-dipole interaction first. An electric dipole moment is described by a vector p. The electrostatic potential energy between two dipoles p and p' a distance r apart is

W = (p.p' -3 (n.p)(n.p'))/r3

where n is the unit vector pointing from one dipole to the other.

Ok similarly, the quadrupole moment of an object is described by a symmetric traceless tensor Q. The electrostatic potential energy between two quadrupoles Q and Q' is given by

W = (Q:Q' -10 n.Q.Q'.n + 35/3 (n.Q.n)(n.Q'.n))/r5

Maybe you'd rather see this written out explicitly with all the indices.

Φ = (QijQ'ij - 10 niQijQ'jknk + 35/3 niQijnj nkQ'klnl)/r5

thank you this exactly what i needed!
 
  • #4
oh,

could you explain to me, why there are 4 indices? i,j,k and l

i thought that this tensor would only use 3 cartesian coordinates?

then why are there 4 different indices?
 
  • #5
Hi, this is very helpful.
could anyone tell me the dipole-quadrupole energy formula?
I have the dipole moment and explicit quadrupole moment terms but aren't sure how to calculate their interaction energy!
 

What is potential energy of quadrupole moments?

Potential energy of quadrupole moments is a measure of the energy stored in a system as a result of the arrangement of charges or dipoles that create a quadrupole moment. It is a type of potential energy in the field of electrostatics and is often used in the study of molecules and atomic nuclei.

How is potential energy of quadrupole moments calculated?

The potential energy of quadrupole moments is calculated using the formula U = -pE, where U is the potential energy, p is the magnitude of the quadrupole moment, and E is the electric field. This formula takes into account the interaction between the quadrupole moment and the electric field.

What factors affect the potential energy of quadrupole moments?

The potential energy of quadrupole moments is affected by several factors, including the magnitude of the quadrupole moment, the distance between charges or dipoles, and the orientation of the quadrupole moment with respect to the electric field. It is also influenced by the dielectric constant of the medium in which the charges or dipoles are located.

What is the relationship between potential energy of quadrupole moments and stability?

In general, the higher the potential energy of quadrupole moments, the less stable the system is. This is because a higher potential energy indicates that there is a stronger interaction between the charges or dipoles, making the system more prone to changes in its arrangement. Lower potential energy usually indicates a more stable system.

How is potential energy of quadrupole moments used in practical applications?

Potential energy of quadrupole moments is used in a variety of practical applications, such as in the study of molecular structures, the development of new materials, and the design of electronic devices. It is also used in the field of nuclear physics to analyze the behavior of atomic nuclei. Additionally, potential energy of quadrupole moments is utilized in the fields of chemistry and biology to understand the interactions between molecules and biological systems.

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