Abstract
The three-body model with central two-body Yukawa interactions is applied to the nuclei 11Li, 14Be and 17B and a long-range effective potential is obtained using the equivalent two-body method for a three-body system. It is first pointed out that the long-range effective potential indicates the effect of the three-body correlation and leads to neutron haloes in these nuclei. Quite good agreement between theoretical results and the experimental data is obtained.