This　study　presents　novel　nanodiamond　composite　films,　in　which　nanodiamond　grains　are　surrounded　by　a　monolayer　heterogeneous　interface.　Calculations　of　diamond　(001)　and　(111)　with　and　without　the　interface　were　conducted　using　the　first-principles　method.　Results　showed　that　silicon　particles　cannot　become　a　solid　solution　in　diamond　crystallites.　Thus,　the　silicon　interface　can　exist　among　diamond　grains.　The　interface　in　diamond　(001)　is　more　stable　than　that　in　diamond　(111).　(C)　2014　Elsevier　B.V.　All　rights　reserved.