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This directory contains a set of dipolar crystals that can be used to |
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test electrostatic computation for dipole-dipole interactions. The |
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dipolar analogues to the structural Madelung constants for ionic |
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crystals were first worked out by Sauer who computed the energies of |
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certain selected dipole arrays (ordered arrays of zero magnetization) |
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and obtained a number of these constants.[1] |
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|
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This theory was developed more completely by Luttinger & Tisza [2] and |
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they tabulated these constants as follows: |
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|
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Array Type Lattice Dipole Direction Energy constants |
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---------- ------- ---------------- ---------------- |
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A SC 001 -2.676 |
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A BCC 001 0 |
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A BCC 111 -1.770 |
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A FCC 001 2.167 |
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A FCC 011 -1.084 |
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|
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B SC 001 -2.676 |
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B BCC 001 -1.338 |
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B BCC 111 -1.770 |
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B FCC 001 -1.084 |
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B FCC 011 -1.808 |
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|
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Type "A" arrays have nearest neighbor strings of antiparallel dipoles. |
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|
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Type "B" arrays have nearest neighbor strings of antiparallel dipoles |
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if the dipoles are contained in a plane perpendicular to the dipole |
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direction that passes through the dipole. |
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|
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Note that these arrays are not necessarily the minimum energy |
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structures, and those interested in this problem should consult the |
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Luttinger & Tisza paper for more details. |
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|
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The electrostatic energy for one of these dipolar arrays is |
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|
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E = C N^2 mu^2 |
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|
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where C is the energy constant above, N is the number of dipoles, and |
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mu is the strength of the dipole. |