Highly Accurate Spectroscopic Parameters from Ab Initio Calculations: The Interstellar Molecules l-C3H+ and C4 PDF
Preview Highly Accurate Spectroscopic Parameters from Ab Initio Calculations: The Interstellar Molecules l-C3H+ and C4
Christopher J. Stein Highly Accurate Spectroscopic Parameters from Ab Initio Calculations The Interstellar Molecules l-C H+ and C 3 4 BestMasters Springer awards „BestMasters“ to the best master’s theses which have been com pleted at renowned Universities in Germany, Austria, and Switzerland. The studies received highest marks and were recommended for publication by supervisors. They address current issues from various fields of research in natural sciences, psychology, technology, and economics. The series addresses practitioners as well as scientists and, in particular, offers guid ance for early stage researchers. Christopher J. Stein Highly Accurate Spectroscopic Parameters from Ab Initio Calculations The Interstellar Molecules l-C H and C 3 + 4 Christopher J. Stein Zurich, Switzerland BestMasters ISBN 9783658148294 ISBN 9783658148300 (eBook) DOI 10.1007/9783658148300 Library of Congress Control Number: 2016945149 Springer Spektrum © Springer Fachmedien Wiesbaden 2016 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. Printed on acidfree paper This Springer Spektrum imprint is published by Springer Nature The registered company is Springer Fachmedien Wiesbaden GmbH Preface As this book contains my masters thesis, it is a summary of the insight I gained in the fieldoftheoreticalrovibrationalspectroscopyofsmallmolecules. Itismoredetailedand descriptive than a research article but certainly less educational than lecture notes or a textbookandthisbookshouldnotbemistakenforanyofthesetypesofscientifictexts. Thewaythemethodsarepresented,however,shouldallowthereadertocomprehendin detailtheindividualstepsthatweretakentoobtaintheresultspresentedhere. Amore detailedunderstandingcanbeachievedwiththeaidofthestandardtextbooksandorig- inalresearcharticlesreferencedwithinthetext. ThetheorydescribedinChapter2and the Appendix should allow students of chemistry or physics and scientists that are new to the field to carry out their own calculations on similar systems and might help them to program their own rovibrational perturbation theory program. Astrochemists might bemoreinterestedintheresultsforthetwolinearinterstellarmoleculesl-C H+ andC . 3 4 Thisworkwasrealizedonlyduetothehelp,knowledgeandpatienceofmysupervisor formorethantwoyears: Prof. Dr. PeterBotschwina. Directlyaftermybachelorstudies heofferedmetoworkinhisgroupasaresearchstudentandteachingassistant. During thistimeinGo¨ttingenIhadthechancetogetafirstinsightintothescientificcommunity, visit international conferences and get to know the process of scientific publishing. He offered all this generously while demanding nothing but an interest in science itself and hisfieldinparticular. Thereisnodoubtthathefuelledmyinterestintheoreticalchem- istry and I am and always will be most grateful for his guidance and support. He died, rather unexpectedly, on December 27, 2014. His death is a great loss for the scientific communityandthestudentsbutbothhavetheirinvaluablememories. IamgratefultomycurrentsupervisorProf. MarkusReiher. Heofferedmeafascinat- ingresearchtopicthatIenjoyworkingoneverydayandanenvironmentthatisextremely motivating. Furthermore,herecommendedmeforSpringer’sBestMasters series. IalsowanttothankProf. RicardoMata, whowasthesecondrefereeformythesisand avaluableadvisorformanydecisionsIhadtotake. ThanksarealsoduetomyformercolleaguesDr. PeterSebald,Dr. RainerOswald,Ben- jaminSchro¨der,ArneBargholzandOskarWeser. Studyingsciencewouldbeimpossible(atleastforme)withoutfriendsthatfindtheright balancebetweenmotivatingmeanddistractingmewithnon-scientifictopics. Inallstages ofmylifeIhadthelucktomeetexceptionallygreatpeopleandIammostgratefultoall ofyou! Ideeplythankmyfamilyandespeciallymyparentswhoseunconditionalsupportand lovearemostprecioustome! Withoutyou,nothingIachievedinmylifewouldhavebeen possible. Contents Preface v List of Tables ix List of Figures xi Acronyms xiii 1 Introduction 1 1.1 Previousexperimentalandtheoreticalresultsforl-C H+ . . . . . . . . . . 1 3 1.2 PreviousexperimentalandtheoreticalresultsforC . . . . . . . . . . . . . 2 4 2 Theoretical methods 7 2.1 Electronicstructuremethods. . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1.1 Singlereferencemethods . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1.2 Multi-referencemethods . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.3 Inclusionofsmallereffects . . . . . . . . . . . . . . . . . . . . . . . 11 2.2 VibrationalPerturbationTheory . . . . . . . . . . . . . . . . . . . . . . . 13 3 Results for l-C H+ 19 3 4 Results for C in its X3Σ− ground state 31 4 g 5 Conclusion and outlook 45 6 References 47 A Appendix 53 A.1 Descriptionof4Lin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 A.2 Forcefieldsforl-C H+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 3 A.3 AdditionaltablesandforcefieldsforC . . . . . . . . . . . . . . . . . . . . 61 4 List of Tables 1 Calculatedequilibriumbondlengthsandequilibriumrotationalconstants forl-C H+. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3 2 Calculatedharmonicvibrationalwavenumbersforl-C H+. . . . . . . . . . 21 3 3 Spectroscopicparametersforl-C H+ obtainedfromcubicforcefields. . . . 22 3 4 Quarticcentrifugaldistortionconstantsofsomelinearinterstellarmolecules. 23 5 Calculatedanharmonicfundamentalwavenumbersandanharmoniccontri- butions∆ =ν −ω forl-C H+. . . . . . . . . . . . . . . . . . . . . . . . . 25 i i i 3 6 Potentialtermsforthebendingcoordinatesofl-C H+. . . . . . . . . . . . 26 3 7 Calculatedspectroscopicparametersforl-C D+. . . . . . . . . . . . . . . . 26 3 8 Calculatedanharmonicconstantsforl-C H+ andl-C D+. . . . . . . . . . . 27 3 3 9 Absolute intensities and wavenumbers for the stretching vibrations of l- C H+ andl-C D+. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3 3 10 BondlengthsandequilibriumrotationalconstantsforC obtainedbyUHF 4 andROHFbasedcompositeschemes. . . . . . . . . . . . . . . . . . . . . . 32 11 Basissetdependenceofbondlengths,equilibriumrotationalconstantsB e andharmonicvibrationalwavenumbersofC asobtainedbyseveralsingle- 4 andmulti-referencemethods.. . . . . . . . . . . . . . . . . . . . . . . . . . 36 12 HarmonicvibrationalwavenumbersforC asobtainedbyComp. 1. . . . 37 4 13 SpectroscopicparametersforC obtainedfromcubicforcefields.. . . . . . 40 4 14 Calculatedanharmonicfundamentalwavenumbersandanharmoniccontri- butions∆ =ν −ω forC . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 i i i 4 15 Anharmonicconstants, quartic force constants in normal coordinatesand quarticforceconstantsininternalcoordinatesforC ascalculatedbydif- 4 ferentmethods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 16 BestestimatetheoreticalvaluesforexperimentallyobservableofC param- 4 etersalongwithexperimentalcounterparts. . . . . . . . . . . . . . . . . . 43 17 Potentialtermsuptoquarticonesforl-C H+ asobtainedbyMRCI(+Q)- 3 F12/VQZ-F12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 18 Potentialtermsforl-C H+ asobtainedbyComp. 1. . . . . . . . . . . . . 59 3 19 Parametersofthestretch-onlyEDMFforl-C H+. . . . . . . . . . . . . . . 60 3 20 CalculatedanharmonicconstantsforC asobtainedbythe“bestestimate”- 4 MRCI(-Q)-F12and+ACPF-F12quarticforcefields. . . . . . . . . . . . . 61 21 Non-redundant potential terms up to cubic ones for C as calculated by 4 differentmulti-referencemethods. . . . . . . . . . . . . . . . . . . . . . . . 61 22 Non-redundant potential terms for C for the basis and smaller contribu- 4 tionsoftheComp. 1method.. . . . . . . . . . . . . . . . . . . . . . . . . 62 23 Non-redundantpotentialtermsuptoquarticonesforC ascalculatedby 4 MRCI(+Q)-F12andACPF-F12. . . . . . . . . . . . . . . . . . . . . . . . 63 List of Figures 1 Specificationoftheinternalcoordinatesforl-C H+. . . . . . . . . . . . . . 19 3 2 PlotsofCCCbendingpotentialsofsomelinearinterstellarmoleculesfrom calculationswiththeComp. 1method,includingf factors. . . . . . . . 24 D 3 Variationoftheelectricdipolemomentforl-C H+ witheachofthethree 3 bondlengths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 4 SpecificationoftheinternalcoordinatesforC . . . . . . . . . . . . . . . . 31 4 5 Cuts through the potential energy surface (PES) of C applying active 4 spacesofdifferentsize. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 6 Effectofsmallercontributionson∆θ,∆21/2S and∆R forC . . . . . . . 39 2 in 4 Acronyms ACPF averagecoupled-pairfunctional CABS complementaryauxiliaryorbitalbasis CASSCF completeactivespaceself-consistentfield CBS completebasisset CC coupledcluster CCSD coupledclusterwithsinglesanddoubles CCSD(T) coupledclusterwithsingles,doublesandperturbativetriples CFF cubicforce-field CI configurationinteraction CSF configurationstatefunction CV core-valence DBOC diagonalBorn-Oppenheimercorrection DF densityfitting DKH2 Douglas-Kroll-Hessmethodatsecond-order EDMF electricdipolemomentfunction HC higher-ordercorrelation HF Hartree-Fock IR infrared ISM interstellarmedium MCSCF multi-configurationself-consistentfield MRCI multi-referenceconfigurationinteraction MRCISD multi-referenceconfigurationinteractionwithsinglesanddoubles MRPT2 multi-referenceperturbationtheoryatsecond-order PEF potentialenergyfunction PES potentialenergysurface
The list of books you might like
