28 HSCDatabases.docx
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28 HSCDatabases.docx
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28HSCDatabases
28.HSC-DATABASES
HSCChemistrycanhandletwoactivedatabasessimultaneously,denotedastheOwnandtheMaindatabase.ThecurrentversionoftheMaindatabasecontainsthermochemicaldataofmorethan20000species,includingpuresubstancesandaqueousspecies.TheOwndatabaseisreservedforthedataspecifiedbytheuser.Itisemptywhentheusergetsthesoftware,butupto60000speciescanbesavedintooneOwndatabase.
AllthecalculationoptionsofHSCChemistryutilizethesamedatabases,andthereforetheyareanessentialpartoftheprogram.Inthedatabasetheenthalpy(H),entropy(S)andheatcapacity(C)valuesoftheelementsandcompoundsaresavedtogetherwithavarietyofadditionalinformation.
NotethatHSCChemistryprimarilyusestheOwndatabase,fileOwnDB6.HSC,ifthesamespeciesisfoundinbothfiles.Itisnotrecommended,therefore,toedittheMaindatabase,fileMainDB6.HSC.ItwouldbemoreconvenienttosavenewdataintotheOwndatabase.AnyvalidfilenamesanddirectoriescanbeusedfortheOwnDB6.HSCandMainDB6.HSCdatabasefiles,andbothcaneasilybechanged.
AllHSCdatabasefilesmayusuallybefoundfrom\HSC6\Databasesfolder.OldMainDB3.HSC,MainDB4.HSCandMainDB5.HSCfilesareincludedwiththenewMainDB6.HSCdatabasefile.Notethatdifferentbasicthermochemicaldatamaycausedifferencestothecalculationresults.Forexample,useofHSCMainDB4.HSCorMainDB5.HSCdatabasefilesmayleadtodifferentcalculationresults.SeeChapter31fordetails.
28.1DatabaseMenu
Fig.1.TheDatabaseMenu.
TheDatabaseMenu,Fig.1,makesitpossibletosearchforthespeciesonthebasisofgivenelements,listspecies,printdata,editolddata,savenewdata,etc.ItcanalsoconvertthermochemicaldatatotheH,SandCpformatsforsavingintheHSC-databases.YoucanselecttheseoptionsbypressingtheappropriatebuttonsintheDatabaseMenu.
28.2NotationsandAbbreviationsusedintheDatabase
Thechemicalformulaearewrittenusingastandardformalismandasbrieflyaspossible.However,therearesomeexceptions,becausesuperscriptsandsubscriptscannotbeused.Thesewillbediscussedinthefollowingparagraphsinmoredetail.SeealsoChapter34.Species,foracompletelistofallthespeciesintheMaindatabase.
Thermodynamicdataforthesolidandliquidphasesofasubstanceisusuallysavedunderthesameformulaname:
forexample,theformulaCucontainsdataforsolid(fcc)andliquidcopper.Gaseoussubstances,however,havetheirownrecordsandtheirnameshavetheextension(g),forexampleCu(g).
Iftheextension(l)isaddedtoachemicalformulaandsuchasubstanceisnotfoundinthedatabasefiles,HSCautomaticallysearchestherecordsfortheliquidphase,extrapolatesitsHandSto298.15K,usingtheCpdataoftheliquid,andsavestheresultswiththeextension(l)intheOWNDB6.HSCfile.Thispermitsextrapolationoftheliquiddatatolowertemperatures.Becareful,however,whenutilizingtheextrapolatedvaluesasthemethodispurelymathematical,especiallyifthetemperatureofyoursystemisfarfromthestableliquidtemperaturerangeofthespeciesconsidered.
Exceptionstothenormalchemicalnotationaretheformulae,whichstartwithastoichiometricnumber.Anextra*character(forexample*2MgO*SiO2)mustbeaddedatthebeginningofsuchaformula.
BecausedifferentcompositioncoordinateshavebeenusedforaqueousspeciesintheHSCdatabase,theymustbedistinguishedfromotherspecieswithasimilarstoichiometry.Thisisdoneusingthesuffix(ending)"a)"withunchargedaqueousmolecules,radicalsandions,forexample:
H+=H(+a)
OH-=OH(-a)
Fe+3=Fe(+3a)etc.
HSCalsocalculatestheelectronicneutralityofthesystemandthereforethesuffix(ending)ofanionizedspeciesmustalsocontainthecharge,forexampleH(+a),OH(-a),Fe(+3a),etc.Ionizedgaseousspeciesarewrittenusingthesimilarformalism:
Ar(+g),H2(+g),etc.Endingscanalsobeusedtodistinguishcompoundswithasimilarchemicalformula,forexample,differentallotropicforms,organicisomers,etc.Herearesomeexamples:
C=Graphite
C(D)=Diamond
C8H10=Dimethylbenzene
C8H10(E)=Octadiyne
Notethattheendingsmustbeinsideparentheses.However,theuseoflower-caseletterss,l,goraisnotallowed,becausetheyarereservedtodistinguishthestatesofmatter,i.e.thesolid,liquid,gasandaqueousstates.
28.2.1HSCFormulaSyntax
Aneasyandillustrativespecificationmethodofspeciesisneededinthermochemicalcalculations.Ininorganicchemistrythisisnotusuallyaproblem,becausetraditionalformulaearequiteshortandillustrative.However,problemsarisewithsomenaturalmineralswithquitelongandcomplicatedformulaeandespeciallywithmanyextremelycomplicatedorganicspecies,forexample:
C6H4(COO(CH2)7CH3CH(CH3)2)2=Diisodecylphthalate.
Speciescouldbeidentifiedusingchemicalnames,buttheseareveryclumsytouse,ChemicalAbstractnumbersarenotillustrative,structuralformulaecouldbeverylongandcrossformulaearenotenough.ThesearethemainreasonsfortheformulasyntaxwhichisusedinHSCChemistry6.0.ThebasicideaofthissyntaxisdescribedinthepreviousChapter28.2andinFig.2.MoredetailsaregiveninthefollowingparagraphsaswellasinChapter29.Hydrocarbonsfortheorganicspecies.
Fig.2.ThechemicalformulasyntaxusedinHSCChemistry6.0.
1.Themaximumlengthofaformulais24characters.Withsimpleinorganicspeciesthetraditionalformulasyntaxcanbeused.However,ifthestructuralformulawithsuffixislongerthan24characters,thenacrossformulamustbeused,seeFig.2.
2.Superscriptsandsubscriptscannotbeused.
3.Innerparenthesesarenotallowed,forexample:
H2(Sn(OH)6)isnotavalidformula,useH2Sn(OH)6,instead.
4.Thelastparentheses,attheendoftheformula,arealwaysreservedforthesuffix,seeFig.2.ThereforeyoucannotusetheformulaAlO(OH).Pleasewriteitinoneofthefollowingways:
AlO2H,AlO*OHorAlO*(OH).
5.Thelasttwocharactersspecifythestateifthelastcharacteroftheformulais“)”.E.g.gas,liquidandaqueousidentifiersmustbeattheendofthesuffix.SeethefollowingexamplesandFig.2:
As(g)Monoatomicarsenicgas
O2(g)Diatomicoxygengas
Fe(l)Liquidiron
OH(-a)AqueousOHion(charge=-1)
6.Gaseousspeciesalwaysneedthe“g)”suffix.Thestateidentifier“s)”isnotusedforthesolidspecies.Normallytheliquidspeciesarealsowrittenwithoutthe“l)”suffix,butsometimesan“l)”suffixmustbeaddedtotheformula.SeeChapter28.11fordetails,becauseincorrectselectionsmaycausebigerrors.
7.Thechargeofanionmustbewrittenjustbeforethestateidentifierwiththecorrectplusorminussign.Forexample:
H(+a),SO4(-2a),O2(-g),etc.,seeFig.2.Thephasecodeaoisusedinthedatabaseforundissociatedaqueousspecies(ions)andaiforaqueouselectrolyte(neutral),whichareformedfromundissociatedaqueousspecies.Notethatthesuffix“ia)”isusedfortheaispeciesand“a)”foraoones.
8.Identicalcrossformulaemustbeseparatedfromeachotherusingtheidentifierjustbeforethechargeandstateidentifiers,seeFig.2.Theseidentifiersshouldbeconstructedfromthenameofthesubstance.Substanceswiththesamecomposition,butdifferentcrystalstructure,caneasilybeseparatedfromeachotherusingonlyonecharacteridentifier.Notethatthemostcommonformofthesubstanceiswrittenwithoutanysuffix.Forexample:
CCarbon
C(D)Diamond
FeS2Pyrite
FeS2(M)Marcasite
Thesituationwithorganicsubstancesisnotassimplebecausethereareanumberofsubstanceswiththesamecrossformula.Thereforelongeridentifiersmustbeused,butitisrecommendedtokeepthelengthoftheidentifiertothreecharacters,seeFig.2.Inmanycasestheidentifiermustbelonger,forexample:
C7H6N2O4(26DNTg)2.6-Dinitrotoluene
C7H6N2O4(34DNTg)3.4-Dinitrotoluene
Numberscanalsobeusedintheidentifier,butthelastcharacteroftheidentifiercannotbeanumber,becauseitmightbeconfusedwithacharge,forexample:
CH2ClBr(CBM+2g),where+2isacharge,seealsoFig.2andChapter29.Hydrocarbons.
9.Theformulabeforethesuffixcanbewritteninmanyways,usuallythesamesyntaxasintheoriginaldatasourceisusedinthemaindatabaseofHSC.However,insomecasesthereisnoestablishedandsettledsyntaxforalltheformulaeandthereforesometimesadiffererentsyntaxhasbeenusedintheHSC6.0database,forexample:
CaMgSiO4=CaO*MgO*SiO2Calciummagnesiumsilicate
MgTi2O5=MgO*2TiO2Magnesiumdititaniumpentaoxide
ThenewFindoptioninthedatabasemenucanbeusedtodisplayalltheformulaewiththesameelementsandstoichiometry,seeFig.1.Theformulacanbewrittenusingnearlyanyconventionalsyntaxtofindthespecieswiththesamestoichiometry.
Anotherusefulfeature,whichisinnearlyallthecalculationmodules,isthepossibilitytocheckthenameofanyspeciesinthedatabaseaswellascollectformulaedirectlyfromthedatabase,seeChapter10.Reactionequations,Fig.10.
10.Theformulacannotstartwithanumbercharacter.Forexample,2MgO*SiO2isnotavalidformula,becausethereactionequationmodulemayconfusethefirst“2”characterwiththestoichiometriccoefficientinareaction.Pleaseaddanasterisk“*”characterontothebeginningofsuchaformula:
i.e.*2MgO*SiO2.
PleasenotethatyoucaneasilycheckthenameandotherdataofaspeciesinmostoftheHSCmodulesbydoubleclickingtheformulainthelistorusingtherightmousebutton.
28.3ReferenceStates
Thereferencestateusedinthedatabasesisthemoststablephaseofthepureelementsat298.15Kand1ba
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