The formations of defective MgCl

2

surfaces

and subsequent adsorption of Ti species and electron donor

as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density functional theory (DFT) method. Twelve possible support models of regular and defective MgCl

2

(110) and (100) surfaces were built. The individual adsorptions of titanium chlorides as mononuclear or dinuclear

and ethyl benzoate (EB) as electron donor

on these models were evaluated. The analysis of energies presented the cases of EB adsorption were generally more stable than titanium chlorides on both surfaces. Thus

EB as internal electron donor mainly prevented TiCl

4

from coordinating on the MgCl

2

surfaces where mostly non-stereospecific active sites could be formed. Exceptionally

A5

the site model with terminal Cl-vacancy on the MgCl

2

support

presented stronger adsorption of TiCl

4

than that of EB on (110) surface. Since the TiCl

4

and ethyl benzoate (EB) would compete to adsorb on the support surface

it seems reasonable to assume that TiCl

4

might predominately occupy this site

which can act as the most plausible active site for propylene polymerization. The first insertion of propylene monomer into the

A5

active site model showed that it exhibited good regioselectivity but poor stereospecificity in the absence of electron donor.