a mold is provided for enabling casting of single crystal metallic articles including a part - defining cavity , a sorter passage positioned vertically beneath and in fluid communication with the part - defining cavity , and a seed cavity positioned vertically beneath and in fluid communication with the sorter passage . the sorter passage includes a shape suitable for encouraging a single crystal structure in solidifying molten metal . additionally , a portion of the mold between the sorter passage and the part - defining cavity includes a notch for facilitating breakage of a cast article proximate the notch during thermal stress build - up , so as to prevent mold breakage or the inclusion of part defects .