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Hi, I was trying to use SHELXD to solve peptide structure. But I got stuck in the input .ins file, and I need some advice. In the .ins file, TITLE CELL ZERR LATT SYMM SFAC C H N O *UNIT* *FIND* *PLOP* NTRY HKLF END A rough estimate, there will be 62 C, 122 H, 14 N, 32 O in one unit cell. 1 for *UNIT* command, *should the following nums be the num of atoms(C H N O) per unit cell and multiplied by 4*? 62x4 for C, 122x4 for H, etc? 2 for *FIND*, the manual says '*estimated num of sites within 20% of true number*', so *should it be 20% of the total number of atoms in one unit cell?* (62＋122＋14＋32)x 20%? 3 for *PLOP*, the manual says *'# of peaks to start with in each cycle, Peaks are then eliminated one at a time until either the correlation coefficient cannot be increased any more or 50% of the peaks have been eliminated' *& '*one should specify more than the expected number of atoms because this procedure involves the elimination of the 'wrong' atoms*' which I don't fully understand,* should the following nums be bigger than the total num of atoms in one unit cell? *Thanks in advance! Lu