In this talk, multiquarks are studied microscopically in a standard quark
model. In pure ground-state pentaquarks the short-range interaction is computed
and it is shown to be repulsive, a narrow pentaquark cannot be in the
groundstate. As a possible excitation, an additional quark-antiquark pair is
then considered, and this is suggested to produce linear molecular system, with
a narrow decay width. This excitation may be energetically favourable to the
p-wave excitation suggested by the other pentaquark models. Here, the quarks
assemble in three hadronic clusters, and the central hadron provides stability.
The possible crypto-heptaquark hadrons with exotic pentaquark flavours are
studied.Comment: 8 pages, 3 tables, talk presented at the International Workshop
PENTAQUARK04 July 20-23, 2004, SPring-8, Japa