This applet models the packing of anions (A, blue) and cations (B, orange) in ionic crystals of a cubic arrangement (8-coordinate), like CsCl.
Click on r+ to increase the radius of the cation, and r- to reduce the radius. The radii of the anions are automatically adjusted, subject to the restraint that two ions can not impinge on each other's space.
The radii of the cation and the anions is displayed in numerical form on the right side of the applet. The ratio of the radius of A to the radius of B is calculated and displayed. Notice that for certain ratios, the space inside the crystal unit cell is used most efficiently. The packing ratio (ratio of the used space to the available space in the unit cell) is calculated and displayed.
The black rectangle displayed denotes the rectangle forms by edges of the cube (on the left and right), and by the diagonal through the face of the cube (on the top and bottom).
© 2004-2011 by Lawrence T. Sein. All rights reserved.
Send questions to: lseinjr@hotmail.com