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Ренер-Телеров ефекат представља вибрационо-електронску (вибронску) спрегу и последица jе нарушавања Борн-Опенхаjмерове апроксимациjе приликом савиjања линеарних молекула са просторно дегенерисаним електронским стањем. Услед савиjаjућих вибрациjа молекула, електронско стање коjе jе просторно дегенерисано при линеарноj геометриjи се цепа на два блиска електронска стања коjа међусобно интерагуjу. Вибронска спрега тада одређуjе ровибрациону структуру спектра молекула, као и могуће понашање молекула у хемиjским реакциjама. У овоj докторскоj дисертациjи проучаван jе Ренер-Телеров ефекат код вишеатомских молекула са произвољним броjем jезгара (више од три jезгра) у Π електронским стањима и линеарном равнотежном геометриjом применом вариjационе методе. За разлику од троатомских молекула где се поjављуjе класични Ренер-Телеров ефекат коjи jе описан у претходном пасусу, код четвороатомских молекула и молекула са већим броjем jезгара уочава се комбинациjа Ренер-Телеровог ефекта и поjаве коничних пресека потенциjалних површи, односно Jан-Телеровог ефекта. Детаљно jе представљен модел за третирање Ренер-Телеровог ефекта и његова поузданост jе тестирана на примеру молекула C2H+ 2 у X 2Π u електронском стању ab initio рачунањем електронских потенциjалних површи и неадиjабатских матричних елемената. Проучена jе топологиjа (избегнутих) пресецања потенциjалних површи и неадиjабатских матричних елемената. У програмском jезику Python написан jе програм за вариjационо рачунање ниско-енергетских вибронских нивоа вишеатомских молекула са произвољним броjем jезгара, линеарном равнотежном геометриjом, Π електронским стањима и произвољне спинске мултиплетности. Конкретно, проучаван jе четвороатомски молекул C2S− 2 у X 2Πu стању. Вариjационо су израчунати вибронски нивои овог молекула и упоређени са доступним експерименталним подацима, при чему jе предложена асигнациjа трака коjе нису биле експериментално асигниране. Даље, топологиjа (избегнутих) пресецања потенциjалних површи и неадиjабатски, The Renner-Teller effect represents а vibrational-electronic (vibronic) coupling and arises as a consequence of violation of the Born-Oppenheimer approximation in linear molecules with spatial degenerate electronic states upon bending vibrations. During bending vibrations of the molecule, a spatially degenerate electronic state at linear geometry splits into two energetically close electronic states that mutually interact. Vibronic coupling could lead to complicated rovibrational spectra of molecules, and also determine their reaction pathways. In this doctoral thesis, we have studied the Renner-Teller effect in linear polyatomic molecules with arbitrary number of nuclei (more than three) in Π electronic states and linear equilibrium geometry by using the variational method. In comparison to the classical Renner-Teller effect in triatomic molecules that was defined in the previous paragraph, in tetra- and any-atomic molecules a combination of classical Renner-Teller effect and appearance of conical intersections of potential energy surfaces occur, i.e. the Jahn-Teller effect. We describe in details a model for treatment of the Renner-Teller effect and test its plausibility on example of C2H+ 2 molecule in the X 2Πu electronic state by ab initio calculations of its electronic potential surface and nonadiabatic matrix elements. Topology structure of (avoided) crossings of potential surfaces and nonadiabatic matrix elements was studied. The program for variational calculation of low-lying vibrionic levels of polyatomic molecules with arbitrary number of nuclei and linear equilibrium geometry in Π electronic states and arbitrary spin multiplicity has been written in Python programming language. We have studied the tetra-atomic molecule C2S− 2 in its X 2Π u electronic state. Vibronic levels of this molecule have been variationally calculated and the obtained results were compared with available experimental data. The assignation of several previously unassigned spectral

In the present paper, the results of combined theoretical and experimental investigation of small non-stoichiometric bromine-doped potassium clusters are reported. Potassium-bromide clusters were obtained by the Knudsen cell combined with surface ionization in the temperature range of 1000–1600 K, and selected by a magnetic sector mass spectrometer. Positive ions of KnBr (n = 3–6) and KnBrn-1 (n = 3–5) clusters were detected for the first time in one set measurement. In order to reveal the geometrical structure of each type of detected cluster, the randomized search algorithm was employed to survey the (Born-Oppenheimer) potential energy surface of both the neutral and cationic KnBr(0,1+) (n = 1–6) and KnBrn-1(0,1+) (n=3–5) clusters, followed by Density functional theory geometry optimizations, and many lowest-energy conformational isomers are presented. From the total electronic energies of clusters computed by the ab initio RCCSD(T)/ECP10MDF(K),cc-pVTZ-PP(Br) method at obtained equilibrium nuclear geometries, the following stability parameters of clusters were computed: their relative energies, the adiabatic and vertical ionization energies, binding energies per atom, and dissociation energies. Both experimental and theoretical results have shown that the title clusters belong to the group of “superalkali” clusters.

Small heterogeneous potassium-iodide clusters are investigated by means of ab initio electronic structural methods together with experimental production and detection in mass spectrometry. Experiments were done by using Knudsen cell mass spectrometry (KCMS) modification method, which provided simultaneous generating of all KnI0,+1 (n = 2-6) clusters at once. Clusters with more than two potassium atoms are produced for the first time. The lowest lying isomers of those KnI0,+1 (n = 2-6) clusters were found by using a random-kick procedure. The best description of growth of these clusters is the addition of one potassium atom to a smaller-neighbor cluster. Subsequently, stability of these species was examined. In spite of general trend of decreasing of binding energies, the closed-shell species have slightly larger stability with respect to the open-shell species. Alternation of dissociation energies between closed-shell and open-shell clusters is presented. Experimental setup also allows determination of ionization energies of clusters: the obtained values are in the range of 3.46-3.98 eV, which classify these clusters as "superalkali." For closed-shell clusters, the theoretical adiabatic ionization energies are close to experimental values, whereas in the case of open-shell clusters, the vertical ionization energies are those that are close to experimental values.

Small heterogeneous potassium-iodide clusters are investigated by means of ab initio electronic structural methods together with experimental production and detection in mass spectrometry. Experiments were done by using Knudsen cell mass spectrometry (KCMS) modification method, which provided simultaneous generating of all KnI0,+1 (n = 2–6) clusters at once. Clusters with more than two potassium atoms are produced for the first time. The lowest lying isomers of those KnI0,+1 (n = 2–6) clusters were found by using a random-kick procedure. The best description of growth of these clusters is the addition of one potassium atom to a smaller-neighbor cluster. Subsequently, stability of these species was examined. In spite of general trend of decreasing of binding energies, the closed-shell species have slightly larger stability with respect to the open-shell species. Alternation of dissociation energies between closed-shell and open-shell clusters is presented. Experimental setup also allows determination of ionization energies of clusters: the obtained values are in the range of 3.46–3.98 eV, which classify these clusters as “superalkali.” For closed-shell clusters, the theoretical adiabatic ionization energies are close to experimental values, whereas in the case of open-shell clusters, the vertical ionization energies are those that are close to experimental values. © 2019 Wiley Periodicals, Inc.

Klasteri su male stabilne ili metastabilne grupe atoma, koje pokazuju zbirna fizička svojstva različita od atoma koji ulaze u njihov sastav. Po osobinama i veličini klasteri se nalaze između molekula i čvrstih materijala. U radu su ispitivana osnovna elektronska stanja malih klastera metala pomoću kvantno-hemijskih metoda, kao i njihova geometrija, hemijska veza i stabilnost. Kao prototip su uzeti homogeni i heterogeni klasteri litijuma – oni su kompjutaciono prihvatljivi, a fizički i hemijski dovoljno kompleksni da se na osnovu rezultata njihovog istraživanja može govoriti o opštim osobinama klastera alkalnih metala. Predstavljeni su rezultati dobijeni pomoću teorije funkcionala gustine (eng. DFT), metode spregnutih klastera [eng. CCSD(T)] i analize vezivnih prirodnih orbitala (eng. NBO). Prikazan je mehanizam rasta ovih klastera, po kojem se formiranje LinX(0,+1) klastera najbolje opisuje dodavanjem jednog atoma litijuma na Lin-1X(0,+1) klastere; sa druge strane, rast klastera pri povećanju broja atoma halogena se dobro opisuje formiranjem LinXm (0,+1) klastera zamenom atoma litijuma halogenim atomom u Lin+1Xm-1 (0,+1). Pokazano je da su vezivne energije po atomu za litijum-halogen klastere veće u poređenju sa homogenim klasterima litijuma. Na osnovu dobijenih rezultata smo zaključili da heterogene LinXm (0,+1) (n = 2-6, m = 1-3, n ≥ m) klastere možemo podeliti na jonske i hiperlitijumske: a) u (LiX)n (0,+1) i katjonskim Lin+1Xn + (n=1,2,3) vrstama svi valentni elektroni su lokalizovani na halogenim atomima, pa se može reći da je u pitanju jonska veza; b) vrste LinXm (n ≥ 2, m = 1-3, n > m) i LinXm + (n ≥ 3, m = 1-3, n > m+1) su hiperlitijumski klasteri – kod njih postoji bar jedan elektron u višku, koji potiče od atoma litijuma, a koji nije predat halogenom elementu. Hiperlitijumski klasteri se mogu predstaviti kao vrste sastavljene od m negativnih halogena X− i pozitivno naelektrisanih Lin (+1,+2) motiva – litijumskih "kaveza". Jonske vrste sa zatvorenom ljuskom, Clusters are small stable or metastable groups of atoms, which exhibit collective properties different from those of constituting atoms, and by general properties clusters are between molecules and bulk materials. The electronic structure of the ground states, geometries, chemical bonds and stability of small metal clusters have been investigated by using methods of quantum chemistry. Homogeneous and heterogeneous clusters of lithium have been taken as the prototype – they are computationally accessible, but physically and chemically complex, enough to make possible the use of obtained results for drawing conclusions about general properties of alkali metal clusters. Results obtained with density functional theory (DFT), coupled clusters method [CCSD(T)], and natural bond orbital (NBO) analysis are presented. The growth mechanism of those clusters is presented; forming of LinX(0,+1) is best described by adding one lithium atom at LinX(0,+1) clusters; on the other hand the growth of clusters with increasing number of halogen atom is good described by forming of LinXm (0,+1) where the lithium atom is replaced with halogen atom in Lin+1Xm-1 (0,+1). It has been shown that binding energies per atom for lithium-halogen clusters are larger than those for homogeneous lithium clusters. Based on our results, heterogeneous LinXm (0,+1) (n = 2-6, m = 1-3, n ≥ m) clusters can be classified as ionic or hyperlithiated: a) in (LiCl)n (0,+1) and cationic Lin+1Xn + (n=1,2,3) species all valence electrons are localized at halogen atoms, thus ionic bond is present; b) LinXm (n ≥ 2, m = 1-3, n > m) and LinXm + (n ≥ 3, m = 1-3, n > m+1) are hyperlithiated clusters – they have at least one excess electron, which originates from the lithium atom, and which is not attracted by halogen. Hyperlithiated clusters can be viewed as species consisting of m negative X− and positively charged Lin (+1,+2) moieties – lithium "cages". Closed-shell ionic species have the largest binding energies, open s

Ispitana je termička stabilnost i mehanizam stupnjevitog razlaganja polinuklearnih kompleksa [(en)(H2O)3Ni - (pyr) - Ni(H2O)3(en)] 4H2O i [Cd(N - Boc - gly)2(H2O)2]n u temperaturskom intervalu od 320 do 760 K. Utvrđeno je da su svi stupnjevi termički aktivirani. Iz površine endotermnih pikova određene su entalpije procesa, a primenom Kissinger-ove metode određena je ukupna vrednost prividne energije aktivacije svakog stupnja razlaganja. Analiza izotermalnih merenja kompleksa nikla ukazala je na sve značajniji uticaj difuzije sa napredovanjem reakcije. Utvrđena je zavisnost reakcionog puta od brzine zagrevanja kompleksa. Analizom promene oblika zavisnosti efektivne energije aktivacije od stepena napredovanja utvrđeno je postojanje reverzibilnog stupnja u procesu dehidratacije kompleksa nikla i promena ograničavaju¢eg stupnja uz sve značajniji uticaj difuzije. Porast, a zatim pad prividne enrgije aktivacije tokom dehidratacije kompleksa kadmijuma i stupnja razgradnje kompleksa nikla ukazuje na promenu ograničavaju¢eg stupnja. Neprekidni porast energije aktivacije razlaganja kompleksa kadmijuma ukazuje da se tokom razlaganjana odvijaju dva paralelna procesa. Vibracione frekvencije izračunate za izokinetičke temperature odgovaraju vibracijama Ni - OH2, Cd - OH2 i Cd - O veza, što je kvantnohemijskim proračunima i određeno. Korelacijom eksperimentalno određenih i izra£unatih termodinamičkih i kinetičkih parametara definisani su mehanizami dehidratacionih i stupnjeva razlaganja oba kompleksa. Proračuni su pokazali da se tokom dehidratacije kompleksa nikla odvija polimerizacija. Pri malim brzinama, polimerizacija pospešuje izlazak vode iz sistema, dok se pri višim brzinama zagrevanja ovaj proces odvija znatno sporije. Ovo uzrokuje postojanje dva reakciona puta na različitim brzinama zagrevanja. Na osnovu proračuna izračunata je konstanta ravnoteže povratnog stupnja na različitim temperaturama tokom dehidratacije polaznog kompleksa. Na ovaj način je pokazano da gubitak kris, Thermal stability and degradation mechanism of [(en)(H2O)3Ni - (pyr) - Ni(H2O)3(en)] 4H2O and [Cd(N - Boc - gly)2(H2O)2]n coordination polymers was investigated in 320-760 K temperature range. It was determined that all of the individual steps are thermally activated. Overall enthalpies of these processes were determined from the area of corresponding endothermic peaks, while the overall average value of activation energies of individual degradation processes were determined using the Kissinger method. The thermal degradation starts with multi-step dehydration process, which exhibits increased influence of diffusion on the reaction mechanism during the progress of the reaction, and its reaction path depends on the heating rate. Analysis of dependence of the value of the effective apparent activation energy on the reaction conversion degree indicates the existence of a reversible step in the dehydration process of Ni-coordination polymer and a change of rate-limiting step of this reaction, probably due to diffusion. Increase and then decrease in the value of the effective apparent activation energy for dehydration reaction of Cd-coordination polymer and degradation reaction of Ni-coordination polymer indicates a change of rate-limiting step, likely due to diffusion of released products. Continuous increase in the value of the effective apparent activation energy for degradation reaction of Cd-coordination polymer indicates that the reaction mechanism consists of two parallel processes. Vibrational frequencies corresponding to the determined values of isokinetic temperatures correspond to Ni - OH2,Cd - OH2 and Cd - O bonds, respectively, and this was confirmed using quantum-chemical calculations. Correlation of experimental and calculated thermodynamic and kinetic parameters has allowed the formulation of the corresponding mechanisms of thermal dehydration and degradation for both of these coordination polymers. DFT calculations indicate that Ni-coordination polymer u

Heterogeni klasteri litijuma tipa LinX (X-halogeni element, n>2) ispoljavaju, zbog svoje neobične stehiometrije, kojom krše oktetno pravilo jer sadrže devet ili više elektrona, specifične osobine. Boldirev et al. su izračunali da pomenuti klasteri imaju niže vrednosti energije jonizacije nego metalni atom koji ulazi u njihov sastav (5,39 eV-3,89 eV). Stoga takve klastere nazivamo “superalkalni”. Pod pojmom “superalkalni” klaster podrazumeva se i potencijalni “gradivni blok” za klasterski-sastavljene materijale sa jedinstvenim elektronskim,optičkim, magnetim i termodinamičkim osobinama. Relevantne eksperimentalne informacije o klasterima tipa LinX su retke i od značaja je pronalaženje mogućnosti za dobijanje ovih vrsta klastera. U ovoj disertaciji, predočena su eksperimentalna i teorijska ispitivanja litijum jodidnih i litijum fluoridnih heterogenih klastera. Ispitivani su uslovi za primenu Knudsenove ćelije kao hemijskog reaktora za istovremeno dobijanje serije klastera tipa LinX (X- F, I, n > 2) i određivanje njihovih energija jonizacije. Eksperimentalni uslovi za dobijanje LinX klastera su optimizirani podešavanjem eksperimentalnih uslova, sastava probe (smeša soli LiF/LiI) i temperature Knudsenove ćelije. Klasteri tipa LinI i LinF (n=2-6) su detektovani u masenom spektrometru iz smeše soli LiF/LiI u kojo je odnos soli iznosio 1:3 and 1:7, respektivno. Litijum jodidni klasteri tipa LinI (n=4, 5, 6) su eksperimentalno detektovani prvi put. Njihove energije jonizacije, koje su određene metodom elektronskog udara, iznose (4,690,25) eV za Li2I, (5,14±0,25) eV za Li3I, (4,860,25) eV za Li4I, (4,62±0,25) eV za Li5I i (4,960,25) eV za Li6I. Litijum fluoridni klasteri Li5F i Li6F su eksperimentalno detektovani prvi put i određene su im energije jonizacije, čije vrednosti iznose (4,29±0,25) eV, (4,24±0,25) eV,respektivno. Prikazane vrednosti energija jonizacije predstavljaju eksperimentalnu potvrdu da klasteri tipa LinX (X-F, I, n =2-6) pripadaju grupi “superalkala”. Pr, The small heterogeneous clusters of the type LinX (X - halogen element, n>2) are of particular importance because these can exhibit unusual stoichiometries, which violate stoichiometry based on the octet rule since they have nine or more valence electrons. Boldirev et al. have calculated that these clusters exhibit lower ionization potentials than those of alkali metal atoms (5,39-3,89 eV); hence they have named “superalkali”. The “superalkali” clusters represent potential “building block” for the cluster-assembly materials with unique structural, electronic, optical, magnetic, and thermodynamic properties. However, relevant experimental information on LinX species is rather scarce, and finding a possibility for obtaining these types of clusters should be important. In this work, we report a combined experimental and theoretical investigation of small heterogeneous clusters lithium iodide and lithium fluoride. It has been investigated conditions for the applicability of Knudsen cell as chemical reactor for simultaneous production of series of clusters of the type LinX (X-F, I, n > 2) and determination of their ionization energies. Experimental conditions for producing of the LinX clusters were optimized by adjustments of the experimental setup, the composition of the sample (the mixture LiF/LiI) and temperatures of the Knudsen cell. The clusters of the type LinI and LinF (n=2-6) were detected in a cluster beam which was generated using the 1:3 and 7:1 mixture of LiF and LiI, respectivelly. The clusters LinI (n = 4, 5 and 6) were detected experimentally for the first time. Their ionization energies determined by the electron impact ionization mass spectrometry were (4,690,25) eV for Li2I, (5,14±0,25) eV for Li3I, (4,860,25) eV for Li4I, (4,62±0,25) eV for Li5I and (4,960,25) eV for Li6I. Also, the clusters Li5F and Li6F were detected experimentally for the first time with their ionization energies of (4,29±0,25) eV, and (4,24±0,25) eV, respectively. These results