Experimentalresults by Fisher et al. [Faraday Discuss. Chem. Soc.1979, 68, 26] showed the existence of local orientationalcorrelations of segmentsof the n-alkane molecules in the liquid state. Sincethe estimated correlation volume is below 103Å3, molecular dynamics simulations appear to be a suitable methodfor their identification and characterization. We used molecular dynamicsto fully characterize short-range order in polyethylene melts. Thecharacterization started by identifying sequences of aligned segmentsin chains, each one having at least one Kuhn monomer in length. Afterward,a search was made for interactions of a tagged aligned chain segmentwith others fulfilling the same condition, laying within a limitingseparation distance (18 Å) and making a limiting orientationangle (40°). When, at least, four interactions are counted, ashort-range ordered region is defined. Chain placement in these regionshas similarities to that of the unit cell at the solid phase, althoughwith different separation distances and angle. Overall, short-rangeorder resembles a dynamic uniaxial nematic phase, the local orderparameter increasing with the chain length in agreement with experimentalresults. Segments at the ordered regions persist over time, for timeslonger than the Rouse relaxation time of the chain. Those in randomconformational sequences between the ordered regions have a mass distributionin agreement with the Flory distribution, with a number-average valuecomparable to experimental results for the molecular mass betweenentanglements. [ABSTRACT FROM AUTHOR]