Nanostructured　surfaces　have　been　proved　to　bring　remarkable　enhancements　in　nucleate　boiling　heat　transfer,　which　are　particularly　attractive　in　thermal　energy　fields.　To　fully　understand　the　effects　of　nano　cavities　on　nucleate　boiling　and　elucidate　the　underlying　enhanced　mechanisms,　a　comparative　molecular　dynamics　study　on　nucleate　pool　boiling　heat　transfer　of　liquid　argon　over　the　plain　copper　substrate　and　nanostructured　substrates　with　different　rectangular　cavities　is　performed.　The　nano-cavities　have　the　same　depth　of　5　nm　and　different　widths　of　3　nm,　5　nm　and　8　nm.　The　bubble　dynamics　behavior　on　various　surfaces　is　observed　based　on　simulation　snapshots.　The　results　manifest　that　the　rectangular　nano-cavity　can　significantly　reduce　time　and　wall　superheat　required　for　the　onset　of　nucleate　boiling,　as　well　as　delay　the　transition　from　nucleation　boiling　regime　to　film　boiling　regime.　The　incipient　nucleation　time　tin　can　be　reduced　to　990　ps　from　5600　ps.　Additionally,　compared　with　the　plain　substrate,　the　rectangular　nano-cavity　can　result　in　a　striking　decrease　in　boiling　initiation　temperature,　which　is　up　to　59　K.　The　underlying　enhanced　mechanisms　are　well　elucidated　based　on　the　structural　feature　of　the　rectangular　nano-cavity　and　simulation　results.　The　liquid　inside　the　rectangular　cavity　can　obtain　additional　thermal　energy　from　sidewalls,　leading　to　a　significant　local　heat　accumulation　effect　and　the　heat　transfer　efficiency　reinforcement.　It　is　found　there　is　a　coupling　enhancement　effect　of　heat　accumulation　when　the　width　of　rectangular　cavity　is　smaller.　Consequently,　the　3　nm　wide　nano-cavity　can　achieve　maximum　enhancement.　These　findings　provide　crucial　evidence　at　the　nanoscale　to　verify　that　nano-cavity　can　significantly　enhance　nucleate　boiling　not　only　by　reducing　nucleation　time　but　also　by　decreasing　the　boiling　initiation　temperature.　This　study　is　of　importance　to　promote　further　insights　into　the　enhanced　mechanism　of　nucleate　boiling　at　the　nanoscale　and　provide　guidance　for　the　performance　improvement　in　boiling　surfaces　for　advanced　thermal　energy　systems.　(c)　2022　Elsevier　Ltd.　All　rights　reserved.