In:
American Journal of Physics, American Association of Physics Teachers (AAPT), Vol. 54, No. 5 ( 1986-05-01), p. 403-405
Kurzfassung:
A purely classical system of four equal point charges q which are free to move over the surface of a sphere is considered. In the equilibrium configuration all charges are located at the vertices of the regular tetrahedron inscribed into the sphere. If a weak uniform electric field E is directed along the z axis, one charge q will move to the position (0,0,R), while three others will form an equilateral inscribed triangle with the plane perpendicular to the field. An increase of the field will distort the tetrahedron [three charges uniformly shift towards the charge at (0,0,R)], keeping the field (z axis) as a C3-symmetry axis. However, when E reaches the ‘‘critical’’ value E0=0.732q/R2, the system abruptly changes its symmetry: For E & gt;E0 the equilibrium (least energy) configuration corresponds to all four charges located symmetrically at the corners of the inscribed square whose plane is perpendicular to E. Consequently, the field will now form a C4-symmetry axis. This jumpwise C3→C4 symmetry change provides a simple classical model for the structural phase transitions when the spontaneous discontinuity arises during a continuous change of one of the intensive variables (in this model the electric field E). Several related open problems which may appear attractive for the modeling on personal computers are also outlined.
Materialart:
Online-Ressource
ISSN:
0002-9505
,
1943-2909
Sprache:
Englisch
Verlag:
American Association of Physics Teachers (AAPT)
Publikationsdatum:
1986
ZDB Id:
1472799-7
ZDB Id:
2947-6
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