  We constructed a simple but effective model to predict the layered
intergrowth structures by combining the self-assembly phenomenon in confined
space and the sandwich configuration of layered materials. In this model, a
two-dimensional confined space is constructed by two known block layers, such
as the Fe$_2$As$_2$ block of iron-based superconductors. Then, the crystal
structure prediction is carried out only inside the confined space to search
for brand-new block layers. We realized this model on the basis of the USPEX9.4
code. In the test, the already existing iron-based superconductors can be
always successfully found, such as Ba$_2$Ti$_2$Fe$_2$As$_4$O,
Sr$_3$Sc$_2$Fe$_2$As$_2$O$_5$, Sr$_4$V$_2$Fe$_2$As$_2$O$_6$, and so on. The
comparison test suggests that our model has remarkable advantages in searching
for intergrowth structures. With this space confinement prediction model, a
structure prediction of layered intergrowth materials even with up to six
elements can be performed with an acceptable machine time consumption. So far,
we have done some multi-composition crystal structure predictions of iron-based
superconductor, and found several stable and metastable structures, such as
Ba$_2$Fe$_2$As$_3$, Eu$_2$Fe$_2$As$_3$, La$_2$O$_2$ClFeAs,
LiOMn$_2$As,Li$_4$OFe$_2$As$_2$.
