分子动力学模拟的建筑材料纳米工程外文文献

分子动力学模拟的建筑材料纳米工程外文文献分子动力学模拟的建筑材料纳米工程外文文献 Contents listsavailable atScienceDirectComposites PartBjournal homepage elsevier locate positesbNano engineering of construction materialsusing molecular dynamicssimulations Prospects andchallengesDenvid Laua b Wei Jiana Zechuan Yua c David Huida Department of Architecture and Civil Engineering City University of Hong Kong Hong Kong Chinab Departmentof Civiland EnvironmentalEngineering Massachusetts Instituteof Technology Cambridge MA02139 USAc Schoolof CivilEngineering andArchitecture Wuhan Universityof Technology Wuhan Chinad Departmentof MechanicalEngineering UniversityofNew Orleans New Orleans LA70148 USAA RT IC LE IN FOKeywords Bio inspired positesCementConcreteFiber reinforced polymersMoleculardynamicsWoodA BS TR AC TInrecent years research articlesinvolving molecular dynamics simulationsof construction materials havegrownsignif i cantly innumber The growthref l ects anemerging needto understandmicroscopic physical and chemicalprocesses which arefundamental tofurther improve the macroscopic performance of construction materials Nano engineering as aconcept aboutmanipulating material structures forcreating newmaterials ormodifyingexisting materials highly dependson the understanding of materials at the nanoscale where moleculardy namics simulationbees an ef f ective andpowerful investigationtool In thispaper the applications of mo leculardynamicssimulations inunderstanding the fundamental deformation mechanism ofvarious constructionmaterials including concreteand cement f i ber reinforced polymersand related bonded systemsupon nano engineering approachare presented In addition the study on naturematerials towards their structuralmor phology and functions atthe atomisticlevel is illustrated so as toinspire the future development of advancedconstruction materials The challengesand innovationsassociated withnano engineering arealso discussed 1 IntroductionThe breakthroughsin nano engineering over the past few decadesenableinvestigations uponintricate phenomenain material systems atthe nanoscale which contributesto the development ofstrengthenedmaterials withunique features As construction materials are closelyrelated toour dailylives andpeople beemore awaretowardssustainability their mechanicalbehaviors especially durability be e the key concern It has been reportedthat mostof constructionmaterialslook goodwhen onlyfocusing on their performance in ashortterm but theycan signif i cantlydeform oreven failupon externalloadings which iswithin itsdesigned capability in naturalenviron ments overa certainperiod of time dueto thedeterioration withinmaterialsor theinteraction between materials andsurroundings 1 3 The materialdeformations alwaysoriginate from the atomisticscale which arehardly noticeableusing traditionaltechniques includingex isting experimentaldetection andcontinuum theory Such anobstaclehas hinderedthe advancementof construction materialsin the past fewdecades untilthe nano engineering concept through simulations hasemerged as anef f ectiveapproach which canreally breakthe icefor theresearch f i eld of construction materials In thepast fewyears suchsimulation approach has been developed signif i cantlyin responseto theincreasingdemand for enhancing construction materials withsatisfac tory performancesand delayeddegradations More importantly the useof nano engineering in the f i eldofconstruction materials can help usdiscovervarious fundamentalfailure mechanismsinside materialsys tems andsuch informationprovides lotsof inspirations for structuraldesign which isbeyond thescope ofcivil engineering The nano engineering employsthe perspectivefrom the nanoscaletowards in depth understanding of underlyingproperties andde formation mechanismsthat governmacroscopicperformanceofcon structionmaterials and theprocedure isimplemented as shown inFig 1 The modelingscheme usingmoleculardynamics MD simula tions for addressing nanostructures and atomisticinteractions insidematerial systems isessential whenapplying the nano engineering ap proach asit isrequired toevaluate atomisticmovements based onmaterial scienceand inherentbehaviors of actual materials MD simu lations serveas ef f ectiveputational experimentsto characterizematerialproperties andpredict mechanical responses which can beused toverify theoreticalhypotheses An earlierdevelopmentof MDsimulation was reported in1950sfora studyon thedynamics of a hardspheresystem consistingof severalhundreds ofparticles 4 Sinces doi 10 1016 j positesb 2018 01 014R eceived19Octoberxx Received inrevised form17January2018 Aepted20January2018 Corresponding author DepartmentofArchitecture andCivilEngineering City Universityof HongKong HongKong China E mail address denvid mit D Lau Composites PartB143 2018 282 2911359 8368 2018Elsevier Ltd All rightsreserved Tthen the advancementof MD simulation has been observedwith theevolutionof putational power in the lastfew decades MDsimu lation representsa powerfultool forpotential applicationsin variousresearchf i elds includingphysics chemistry biology bio engineeringand medicine 5 6 Recently ef forts have been madefor applyingthemethod to thef i eldsof structuralmechanics andcivil engineering Traditionally the classicalcontinuum mechanicstheories have been thebasis for mostputational methodsused invarious engineeringf i eldsincluding civiland mechanicalengineering examples aref i niteelement analysis f inite dif f erencemethod f inite volumeand boundaryelementmethods The capabilityof the continuum approachis limitedwhenstructural solutionat asmall length scale isof concern In otherwords the predictionsabout materialbehavior should be madefrom afundamentalbottom up perspective In MD simulations materials can be treatedas aggregationof atomswhich are regardedas classical non quantum and subjected toNewton s Lawsof motion mass particles This methodis based ontrajectory ofatoms inthe modelingsystem andcan providedata thatinvolvestime evolutionof materialnanostructures subjected to externalconditions Basically the putationinvolves iterativemanipulationof threeimportant parametersincluding displacement position velo city and aeleration as the solutionof Newton s secondlaw To im provethecalculation ef f i ciency inthe iterativeprocessing dif f erentnumerical methods have beendeveloped for example Verlet integra tion leapfrog integration velocity Verletintegration andpredictor corrector integration 6 These algorithmshave theirown strengthsandweaknesses and arefeasible to be employedfor dif f erentmaterials The forcef i eldplays an important role in describinginteratomic inter actions and theselection of forcef i eld criticallydetermines thevalidityof MD simulations A numberof widelyused forcef i eldshave been in troduced fordif f erent kinds of material systems 7 10 These force f i elds targetfor eitherinorganic ororganic polymers while nodirectdescription forgeneral construction materials is available The monfunctionalterms includinggeneral bondedand non bonded energiesfrom these forcef i eldshave beenadopted in construction materialsasthe formulationof interactionscan beshared insimilar structures Forthe MD simulations withoutany chemical reaction the non reactiveforcef i elds can be employedto describe the interactions between dif ferent ponentsinthematerial systems However the connectivityamongponents canbe alteredin specialconditions associatedwithrelease ofatoms as well asgeneration ofnew phase i e involvingchemistry where thenon reactive forcef i eldsare nolonger available To simulatebond breakingand bondformation inmaterial systems thereactive forcef i eldsuch asReaxFF 10 canbeused The reactiveMDenables theinvestigations ofchemicalreactionmechanisms includingcatalysis pyrolysis andbustion The enrichmentof forcef i eldsforvarious interactionssatisf ies theneed ofdescribing theinteractionsbetween dissimilarponents as well asbetweenmaterials and ex ternal surroundingssuch aswater orother moleculesin solventenvironments which causethe structuralchange in constructionma terialsandaf f ect materialproperties in a longrun The resultsgener ated fromMD simulationscan providethe keymissing knowledge oftraditional construction materials atmolecular level which has beenusually overlookedfor thepastfewdecades When applyingMD simulationsinconstruction materials research there arecritical challengescovering howto extractinformation duringphysicaland chemicalprocesses from the nanoscale and torelate thenanoscaleinformation to the macroscopicmaterial performance Although MD simulations have been widelyapplied on the studyofconstruction materialsoverthepastfewyears this putationalap proachhas a limitationin both the time scale and the length scale Inview ofsuch asmall magnitudeof timeand lengthscale which aregenerallynanosecond 10 9s and nanometer 10 9m MDsimula tions arenot suitablefor directlystudying construction materials astheyare alwayslarge inlengthscaleand theirperformancein a longrunis alwaysthekeyforasustainable design To resolvethe limitationinboththelengthscaleand thetimescale the multiscale modeling forconstructionmaterials is proposed that can linkMD resultsto micro scopic observationssoasto interpretmaterial behaviors Recent ad vances inputationalpowerand algorithmshave increasedthetimescales forcapturing materialbehaviors overmillisecond scale These limitationsfurther motivatethedevelopmentof applyingnano engineering conceptinconstructionmaterials In thispaper thenano engineering approachusing MD simulationson thestudies ofconstructionmaterials as well as therecent progressonthe fundamental understandingofconstructionmaterialsand theirbe haviors is reviewedwith anemphasis onthe linkagebetween thena noscale and the macroscale and thetransition fromresearch topracticalapplications Widely usedconstructionmaterialslike concrete f i berre inforced polymer FRP and theirrelatedbonded structures areselectedas representativematerialsystemshere For theselected materialsys tems atomistic modeling forcef i eld selection and simulationdetailsunder dif f erentconditions areintroduced and evaluated MD simulationsdemonstratinghow physicaland chemicalprocesses behindmacroscopicmaterial performanceare presented In addition the state of the art re lated tobio inspired materialsprovides anew insighttowards thefutureresearch directionfor constructionmaterials It isenvisioned that thedevelopment ofconstructionmaterialsshouldbefounded onthe activelearningfrom thenatural featuresof biomaterials The crucialchallengesof nano engineering approachusing MD simulations arealso addressed which areimportant forour futureresearch anddevelopment This re view demonstratesthe capabilityof nano engineering forresearch ofconstructionmaterials which isa breakthroughfrom thetraditional ideawhichnormally sticksto theinvestigations ofconstruction materialsusingmacroscale modelsonly toan innovativeapproach whichin tegrates twoextreme and disconnected f i elds i e discrete versuscon tinuum as awhole The prehensiveknowledgeof the existingre searchf i ndingsand theclear understandingupon thelimitations canaeleratethe progressof nano engineering forconstructionmaterials 2 Concrete andcementAs aplex posite concrete consistsofabinding phase ce ment matrix andaparticulate phase aggregates In normalstrengthconcrete the particulatephase ismuch strongerthan thebinding phase Therefore mechanical properties of concretelargely dependon thecement matrix In thisposite materialsystem the cementmatrix isthekey focusof MD simulations which containsfour majorpo nents asshown in Fig 2 All of these ponentsreact withwater togeneratehydration products Nanostructures hydration processesandmechanical properties of theunhydrated clinkersas wellas hydrationproductsare ofmajor interests Besides theanalysis ofmaterialstruc tureandbasic mechanical properties thenano engineering approachisparticular usefulto facilitatethe studyoftime dependent behavioranddecode thenanogranular originof creepin concrete 11 Fig 1 Proposed implementationofnano engineering processesforenhancingmaterialproperties D Lau etal Composites PartB143 2018 282 2912832 1 Cement mineralsCementmaterialsystem is reviewedfollowing thebottom up con cept Atomistic models of cementponents aredeveloped basedonexperimental characterizations With aproper selectionof forcef i eld MDsimulations canbe performed and materialproperties canbe calculated Understanding materialbehaviors atthenanoscalepaves theway toimprovestrength anddurability of cement based materialsby nano en gineering approach For example knowing molecularstructures ofre active ponentsin cementclinkers maycontribute tosearching sup plementary cementitiousmaterials SCM for sustainabilityconcerns Tricalcium silicate C3S dicalcium silicate C2S tricalcium alu minate C3A and tetra calcium aluminoferrite C4AF are fourmajorminerals inordinary Portlandcement OPC powder At thenanoscale their mechanicaland chemicalproperties canbe studiedvia MDsi mulations The startingpoint of MD simulationslies onthe molecularstructuresof theseminerals incrystalline forms which areoften re solved byX ray crystallography Another basisofMD simulations isareasonably aurateforcef ield thatcan describe interactions betweenatomsof theminerals which covercalcium silicon oxygen hydrogen aluminum andiron Among theseminerals C3S C2S andC3A have beensuessfully modeled and simulated Those reportedworks areusefulreferences thatfacilitates modelconstructions infuture MD simulations 12 17 C3S or alite aounts for around50 weight ofOPC powder Threekinds ofstructural familiesof C3S arefound 12 A forcef ieldthat canreproducereasonable surfaceand interfaceproperties isdeveloped 18 which ispatible withmany othermonly employedfor cef ields Dissolution mechanismsat crystalsurfaces withdiff erentcleavages areinvestigated byReaxFF based simulations 19 Fracturemechanics andreactivity havebeen studied 6 by usingClayFF po tential This studyalso includesa parisonamong differentforce f ields andit isshown thatClayFF isa veryef f ective onefor large scalesimulations Hydration of C3S withsubstitutional impuritieshas beenstudiedvia densityfunctional theory DFT calculations and ReaxFFsimulations 20 At arelatively largescale MD modelingof cementpasteasatwo phase positesystem which includeshydrated andunhydratedphases isproposed 21 This modelcaptures hetero geneous featuresof cement paste andcan representcementpastera tionally C2S is also calledbelite andit aountsforaround20 weight ofOPCpowder Five types of C2S polymorphsare identif i edasre presentative models 13 14 Based onthe atomistic structuresand theClayFF potential MD simulationsare performedto characterizecrys talline propertiesof thisstructurally plexmaterial C2S At thesurface of C2S electronic structuresand adsorptionenergy surfacecanbe putedvia DFTcalculations 22 Behaviors of water moleculescanbe simulatedby usingReaxFF 22 Ef f ect ofpolycarboxylate ether based PCE superplasticizer on C2S substrateis investigated byPASS based MD simulations 23 Substitution ofmetal ionsat thesurfaceof C2S isalso investigatedby DFTcalculations andforcef ieldsimulations basedon core shell potentialmodel 24 C3A andC4AF areminor phasesin OPCpowder In thepast decade there are some simulations onC3A andfew MD simulations onC4AF Structural and elastic propertiesof C3A crystalscanbefound intheexisting literature 15 17 PASS universal forcef ield UFF andDreiding forcef ieldhavebeenevaluated uponits feasibilityfor cementapplication 15 Recently focal pointofMDsimulationsoncement hasbeenput onhydration productsof alite belite andC3A The hydrationproductsare constituentsof hardenedcement andarecloselyrelated tothe mechanical performanceofcementaswellas concrete Among thehydrationproducts calcium silicate hydrate C S H is regardedas themostimportant bindingphase 2 2 Hydration productsCalcium silicate hydrate C S H oupies morethan50 volume inthepaste andisamajor ponentof hardenedhydrated cementpaste C S H providescohesive forceto hardenedcement andis regardedasthe mostimportant hydrationproducts in cement Atomistic modelsofC S H arederived fromexperimental characterizations which mainlyinvolvewater content Ca Si ratio density tetrahedral coordinationofsilicate aswellasmicromechanical tests Forcef ields includingPASS 9 ClayFF 25 CSH FF 26 andReaxFF 27 have beenused The INTERFACEforcef ield an extensionof thesemon for cef ields has also beendevelopedfor theinteractions atthe inorganic organic andinorganic biomolecular interfaces 28 The positionofdif ferent phasesin C S H playsanimportantrole inthe structure andmechanical properties 29 30 Therefore an auratemodel isre quired inMDsimulationsfor nano engineering approach Models de rived fromtobermorite andjennite arereasonable representativesof C S H 31 35 Based onthose pilotworks inmodeling differentcon stituents within C S H the breakthroughofafull atomisticmodel for C S H has been reported 36 The suessof thisrealistic modelenablesthe studieson deformation and crackingafter loadingfromthena noscale which arehistorical problemsduring theservice lifeofcon crete and thedetailed atomisticdescription contributesto themulti scalemodelingforC S H 37 Still there isno stopon theimprovementof C S H models 38 41 A colloidalmodel usingsphe rical particlesis applied to probethe multidomaincharacter andme chanicalresponse of C S H which indicatesthe relationshipbetweenpacking fractionandelasticproperties 42 The coarse grained CG models arebuilt usingdisk like buildingblocks derivedfromtheas sociated atomisticmodel It isshown thatthe CG models aremore re lated to the experimentalobservation andcan linkup with the mac roscopic propertiesof concreteseamlessly 43 44 As mentionedbefore hydration issignif icant inC S H and theunderstandingof thisprocesshelps tounravel the structureandmechanicalpropertiesofcement 45 46 The hydrationof calciumoxide incontact withdif ferent amountof waterhas beenstudied usingreactive forcef ield showing therole ofwater inremaining thesurface structure 47 Water sor