The structure and relative stability of the most stable isomers of different families of (H2O)(20) clusters viz. edge-sharing pentagonal prism, face-sharing pentagonal prism, fused cube, dodecahedron and irregulardodecahedron are studied using dispersion corrected density functional Becke97-D in conjunction with cc-pVTZ basis set. The relative stability of water clusters followed the order ESPP > FSPP > FC > DD > IDD. It is found that the relative stability depends mainly on degree of fusion, number of AADD water molecules and four-membered rings present. For a given family, the energy of isomers increases with decrease in the number of tld hydrogen bonds. (C) 2015 Published by Elsevier B.V.