Density functional theory (B3LYP/6-31G*) and classical molecular dynamics simulations on the alkali metal cation oscillation/migration through the 1,3-alternate calix[4]arene cavity have been carried out to evaluate the barrier for the process. The estimated DeltaG(not equal) of 15.22 kcal/mol for the migration of K+ ion through the pi-tube of the tetrakis(ethoxyethoxy)calix[4]arene (TEC) in methanol is comparable with the experimental value of 13.2 kcal/mol in dichloromethane-methanol mixture. The barrier for the oscillation of Cs+ along the pi-tube of 1,3-alternate calix[4]arene-bis-crown-5 (BC5) is much higher by about 20 kcal/mol (DFT) or 15 kcal/mol (MD) than that for the K+-oscillation. (C) 2003 Elsevier B.V. All rights reserved.