lattice $Lx=192$, $Ly=336$, is shown in the inset. []{data-label="figure9"}](fig9){width="7cm"}

Temperature dependence of the structure factors were calculated using MC simulation and changing temperature in the way described in Sec. \[s3\]. Most of simulations were performed on the lattice with $Lx=90$, $Ly=132$. The spots of disordered phase have the same diffracted intensities. Their temperature dependence (see Fig. \[figure9\]) on warming and on cooling shows the presence of hysteresis loop in behaviour of $S(T)$ close to the phase transition what is in agreement with experimental results [@song95]. The hysteresis loop calculated for large lattice with $Lx=192$, $Ly=336$ is shown in the inset in Fig. \[figure9\]. There are several points where the structure factor takes intermediate values because at these temperatures coexistence of faceted and disordered phases has been observed. More coexistence points where found on warming than on cooling. We observe also discontinuity of the structure factor at the transition temperature. Thus hysteresis and discontinuity of the structure factors are another argument for the first-order phase transition between faceted and disordered phases. During the process of warming up the system the S decreases with temperature and becomes very small when on the surface large enough {211} facets are formed.

![ Temperature dependence 