The present work investigates the relationship between the growth kine
tics and the crystal structure of N-methylurea (NMU) crystals. Anisotr
opy of the step kinetic coefficient, step free energy, and normal grow
th rate of NMU crystals may be explained on the basis of a model which
links the above quantities with the energy of kink formation in the g
rowth steps. The proportionality condition between the solid-solid and
solid-liquid bonds has been applied, and the coefficient of this inte
raction was obtained experimentally. The anisotropy of the crystal hab
it observed in these experiments is much greater than that predicted b
y the attachment energy model. We suggest that the method may be gener
ally used to quantify the crystal growth anisotropy of molecular cryst
als.