Two kinds of anion clusters, i.e.,H-4PO-4~- and H-4P-2O-~28 are constructed, by bonding two and four anions. The optimized configurations, vibrational frequencies and Raman activities of H-2PO- 4 , H-2PO-8~2- and are obtained by using density functional theory. The Raman scattering spectra in the solid- liquid interface boundary layer are measured , and compared with those of theoretical calculation for studying the configuration and the processes of polymerization and dehydration etc . Both the experimental and theoretical results indicate that dimmer clusters may be the growth units in crystal growth , which can polymerize further and form polymer cluster on the solid-liquid surface . The dehydrating process of dimmer and polymer clusters starts at a growth layer about 50 jura apart from the solid- liquid surface of the KDP crystal. With approaching to the crystal- liquid surface, the molecular .cluster becomes more and more orderness . The results obtained are of significance in identifying the surface kinetics process and developing more sophisticated crystal growth theories

Key words: density functional theory, RAMAN SPECTROMETRY, CRYSTAL GROWTH, CONFIGURATION