Ultrafine particles of pure iron were produced by evaporation method and their average sizes estimated are 25, 50, 90, and 120 nm using the laser particle analyzer. assuming that the resultant particles are strain free and the peak broadening detected in the measurement with cu-ka radiation arises only from variation of size of the crystallites, estimate the peak width (the value of fwhm) of the (110) plane detected by using the scherrer equation. lattice constant of pure iron is 0.287 nm.