Molecular　and　density　distributions　of　the　lubricant,　pentaerythritol　tetraheptanoate　(PEC7),　confined　to　a　nanogap　were　investigated　using　molecular　dynamics　(MD)　simulations　at　various　temperatures,　initial　film　thicknesses　and　pressures.　All　of　the　simulated　film　thicknesses　were　less　than　10.　nm.　The　PEC7　molecular　orientation　and　density　profiles　were　analyzed,　and　the　simulated　densities　were　compared　with　empirical　bulk　fluid　densities.　The　results　show　that　the　PEC7　atoms　tend　to　form　two　or　three　layers　near　every　confining　wall,　but　the　PEC7　molecules　orient　randomly　throughout　the　film.　The　lubricant　density　profiles　are　found　to　fluctuate　frequently,　and　the　distances　between　the　layers　of　lubricant　atoms　are　irregular.　Furthermore,　the　equivalent　density　is　lower　for　films　with　a　thinner　initial　film　at　the　same　pressure　and　temperature,　but　the　compressibility　is　similar　for　films　with　different　initial　film　thicknesses.　The　simulated　densities　with　an　initial　film　thickness　of　9.32.　nm　are　in　agreement　with　the　values　obtained　from　the　Tammann-Tait　equation,　with　deviations　less　than　5%.　The　MD　simulation　can　not　only　predict　the　bulk　compressibility　of　the　lubricant　but　also　provide　information　on　the　density　and　molecular　distribution　within　a　thin　film,　which　cannot　be　obtained　from　experiments.　©　2014　Elsevier　B.V.