1 |
gezelter |
1889 |
This directory contains a set of dipolar crystals that can be used to |
2 |
|
|
test electrostatic computation for dipole-dipole interactions. The |
3 |
|
|
dipolar analogues to the structural Madelung constants for ionic |
4 |
|
|
crystals were first worked out by Sauer who computed the energies of |
5 |
|
|
certain selected dipole arrays (ordered arrays of zero magnetization) |
6 |
|
|
and obtained a number of these constants.[1] |
7 |
|
|
|
8 |
|
|
This theory was developed more completely by Luttinger & Tisza [2] and |
9 |
|
|
they tabulated these constants as follows: |
10 |
|
|
|
11 |
|
|
Array Type Lattice Dipole Direction Energy constants |
12 |
|
|
---------- ------- ---------------- ---------------- |
13 |
|
|
A SC 001 -2.676 |
14 |
|
|
A BCC 001 0 |
15 |
|
|
A BCC 111 -1.770 |
16 |
|
|
A FCC 001 2.167 |
17 |
|
|
A FCC 011 -1.084 |
18 |
|
|
|
19 |
|
|
B SC 001 -2.676 |
20 |
|
|
B BCC 001 -1.338 |
21 |
|
|
B BCC 111 -1.770 |
22 |
|
|
B FCC 001 -1.084 |
23 |
|
|
B FCC 011 -1.808 |
24 |
|
|
|
25 |
|
|
Type "A" arrays have nearest neighbor strings of antiparallel dipoles. |
26 |
|
|
|
27 |
|
|
Type "B" arrays have nearest neighbor strings of antiparallel dipoles |
28 |
|
|
if the dipoles are contained in a plane perpendicular to the dipole |
29 |
|
|
direction that passes through the dipole. |
30 |
|
|
|
31 |
|
|
Note that these arrays are not necessarily the minimum energy |
32 |
|
|
structures, and those interested in this problem should consult the |
33 |
|
|
Luttinger & Tisza paper for more details. |
34 |
|
|
|
35 |
|
|
The electrostatic energy for one of these dipolar arrays is |
36 |
|
|
|
37 |
|
|
E = C N^2 mu^2 |
38 |
|
|
|
39 |
|
|
where C is the energy constant above, N is the number of dipoles, and |
40 |
|
|
mu is the strength of the dipole. |