TY - THES A1 - Topaj, Dmitri T1 - Synchronization transitions in complex systems N2 - Gegenstand dieser Arbeit ist die Untersuchung generischer Synchronisierungsphänomene in interagierenden komplexen Systemen. Diese Phänomene werden u.a. in gekoppelten deterministischen chaotischen Systemen beobachtet. Bei sehr schwachen Interaktionen zwischen individuellen Systemen kann ein Übergang zum schwach kohärenten Verhalten der Systeme stattfinden. In gekoppelten zeitkontinuierlichen chaotischen Systemen manifestiert sich dieser Übergang durch den Effekt der Phasensynchronisierung, in gekoppelten chaotischen zeitdiskreten Systemen durch den Effekt eines nichtverschwindenden makroskopischen Feldes. Der Übergang zur Kohärenz in einer Kette lokal gekoppelter Oszillatoren, beschrieben durch Phasengleichungen, wird im Bezug auf die Symmetrien des Systems untersucht. Es wird gezeigt, daß die durch die Symmetrien verursachte Reversibilität des Systems nichttriviale topologische Eigenschaften der Trajektorien bedingt, so daß das als dissipativ konstruierte System in einem ganzen Parameterbereich quasi-Hamiltonische Züge aufweist, d.h. das Phasenvolumen ist im Schnitt erhalten, und die Lyapunov-Exponenten sind paarweise symmetrisch. Der Übergang zur Kohärenz in einem Ensemble global gekoppelter chaotischer Abbildungen wird durch den Verlust der Stabilität des entkoppelten Zustandes beschrieben. Die entwickelte Methode besteht darin, die Selbstkonsistenz des makroskopischen Feldes aufzuheben, und das Ensemble in Analogie mit einem Verstärkerschaltkreis mit Rückkopplung durch eine komplexe lineare Übertragungssfunktion zu charakterisieren. Diese Theorie wird anschließend für einige theoretisch interessanten Fälle verallgemeinert. N2 - Subject of this work is the investigation of generic synchronization phenomena in interacting complex systems. These phenomena are observed, among all, in coupled deterministic chaotic systems. At very weak interactions between individual systems a transition to a weakly coherent behavior of the systems can take place. In coupled continuous time chaotic systems this transition manifests itself with the effect of phase synchronization, in coupled chaotic discrete time systems with the effect of non-vanishing macroscopic mean field. Transition to coherence in a chain of locally coupled oscillators described with phase equations is investigated with respect to the symmetries in the system. It is shown that the reversibility of the system caused by these symmetries results to non-trivial topological properties of trajectories so that the system constructed to be dissipative reveals in a whole parameter range quasi-Hamiltonian features, i.e. the phase volume is conserved on average and Lyapunov exponents come in symmetric pairs. Transition to coherence in an ensemble of globally coupled chaotic maps is described with the loss of stability of the disordered state. The method is to break the self-consistensy of the macroscopic field and to characterize the ensemble in analogy to an amplifier circuit with feedback with a complex linear transfer function. This theory is then generalized for several cases of theoretic interest. KW - Synchronisierung KW - komplex KW - System KW - komplexe Systeme KW - gekoppelt KW - chaotisch KW - Chaos KW - Interaktion KW - Übergang KW - P hasensynchronisierung KW - Phase KW - Feld KW - Effekt KW - synchronization KW - complex KW - system KW - complex systems KW - coupled KW - chaotic KW - chaos KW - interaction KW - transition KW - phase KW - phase synchronization KW - field KW - meanfield KW - o Y1 - 2001 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-0000367 ER - TY - GEN A1 - Opfer, Björn T1 - Organisiertes Verbrechen und politische Transformation in Bulgarien T1 - Organized crime and political transformation in Bulgaria N2 - Since the late 1960s of the 20th century, Bulgaria experienced a great increase in organized crime. As a result, relations between the managers of state-owned enterprises, the state security service, party officials, and criminal actors grew and became stronger. Parts of the old network are still functioning. Through the support of governmental circles, organized crime became established and dominated essential parts of the economy, from the mid-1990s. Since 1996, however, governments tried to act against organized crime. The influence of the mafia is still an unsolved problem and a challenge to the transformation of the country. KW - Bulgarien KW - Wechsel KW - organisiertes Verbrechen KW - politische Eliten KW - Bulgaria KW - transition KW - organized crime KW - political elites Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-47418 ER - TY - GEN A1 - Geiß, Paul Georg T1 - Regionalismus und Staatlichkeit in Turkmenistan T1 - Regionalism and statehood in Turkmenistan N2 - Regionalism in Central Asia is often identified with the dominance of tribal affiliations in politics. This classification, however, is problematic because it neglects the extent of social change under the Soviet rule. In Soviet Turkmenistan state structures were relatively strong. However, personal relations within the Communist party had preserved patrimonial elements within the state. The dissolution of the Soviet Union led to a stronger patrimonialization of authority relations. In Turkmenistan, this process led to an extreme form of a neo-patrimonial state due to the personal and arbitrary rule of its president Nijazov. KW - Zentralasien KW - Wechsel KW - neopatrimonialer Staat KW - Regionalismus KW - Central Asia KW - transition KW - neo-patrimonial state KW - regionalism Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-11650 ER - TY - GEN A1 - Hensell, Stephan T1 - Regieren in Albanien : Herrschaftslogik und Zerfall eines Familienstaates T1 - Peripheral states in Eastern Europe : patrimonial socialism and its transformation N2 - Taking into account historical as well as sociological differences, the author distinguishes between different modes of socialism. On the periphery of the Soviet Union and Eastern Europe, the combination of modern and traditional elements led to the establishment of hybrid political forms. They could be characterized as bureaucratic-patrimonial and associated with a specific type of state: the "peripheral socialist state". KW - Übergang KW - Hybridstaat KW - bürokratisch-ererbter Staat KW - Vetternwirtschaft KW - transition KW - hybrid state KW - bureaucratic-patrimonial state KW - clientelism Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-11660 ER - TY - GEN A1 - Koehler, Jan A1 - Zürcher, Christoph T1 - Der Staat und sein Schatten : zur Institutionalisierung hybrider Staatlichkeit im Süd-Kaukasus T1 - The state and its shadow : institutionalisation of hybrid states in the southern Caucasus region N2 - This article looks at contemporary Armenia, Georgia, and Azerbaijan and addresses the question of how these states, which suffer from considerable institutional weaknesses, nevertheless retain the ability to control key aspects of statehood, first of all security and a measure of central authority. It is argued that these states invest only in selected aspects of statehood. The needed resources are mobilized by a system of informal taxes, which are then invested in certain selected core functions of statehood. This form of state depends on both formal and informal institutions, which are mutually supportive. KW - Georgien KW - Armenien KW - Aserbaidschan KW - Wechsel KW - Staatsaufbau KW - Georgia KW - Armenia KW - Azerbaijan KW - transition KW - state-building Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-47422 ER - TY - GEN A1 - Aphrasidze, David T1 - Die Polizei in Georgien : Wandel eines Akteurs T1 - The police in (Post-Soviet) Georgia : change of an actor N2 - During the violent phases of transformation in post-Soviet Georgia the power of the police passed on to paramilitary groups. Under the rule of president Shevardnadze, however, the police regained a central political role, but it remained embedded in Soviet and pre-Soviet political structures. This becomes visible by looking at the political economy of the police. Informal taxes, purchase of office, and clientelism became established practices within the police. At present, the new government tries to carry out structural reforms in the police sector, which might lead to a break with the current hybrid Georgian state model. KW - Georgien KW - Wechsel KW - Hybridstaat KW - Polizei KW - Georgia KW - transition KW - hybrid state KW - police Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-47390 ER - TY - GEN A1 - Berg, Andrea T1 - Dynastie oder Demokratie? : Die Personalisierung des Staates in Zentralasien T1 - Dynasty or democracy? : The personalisation of the state in Central Asia N2 - The increasing concentration of power in the hands of the presidential families in all Central Asian states led to the personalisation of the state during the last years. The presidents successfully established neo-patrimonial, authoritarian regimes with a high level of consolidation but without fulfilling the criterion of democracy. The article explores the strategies the presidents use to maintain their authority and discusses which political developments can be expected concerning the question of succession. KW - Zentralasien KW - Wechsel KW - Hybridstaaten KW - neopatrimoniale Regierungen KW - Central Asia KW - transition KW - hybrid states KW - neo-patrimonial regimes Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-47405 ER - TY - GEN A1 - Heinz, Wolfgang S. T1 - Militär und Transition zur Demokratie in Lateinamerika : ein Rück- und Ausblick T1 - Military and transition to democracy in Latin America N2 - Since the beginning of the 1970s a lot of countries in Latin America has been starting the transition to democracy. The article analyses the role played by the military in this process, especially the effects of civildemocratic governments – sometimes failing in – gaining power over the military. It is described how and why the army occasionally kept their independence from the civil power and how this influenced the consolidation of democracy. KW - Lateinamerika KW - Militär KW - Übergang KW - zivil-militärische Beziehungen KW - Demokratie KW - Latin America KW - military KW - transition KW - civil-military relations KW - democracy Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-48299 ER - TY - GEN A1 - Radseck, Michael T1 - Die vernachlässigte Reform : zum Primat der Politik über das Militär im südlichenLateinamerika T1 - Neglected : civilian control over the military in Latin America N2 - Despite many economic and state reforms in South America, no comparable changes have taken place with regard to civil-military relations: Neither do the armed forces have a clearly defined mission of their own nor are they adequately democratically controlled. The article looks at the present civil-military relations from various angles and explicitly deals with examples from Argentina, Bolivia, Chile and Peru. It presents the reasons for the lack of civilian control over the military and discusses the resulting consequences for domestic and foreign politics. KW - Lateinamerika KW - Veränderung KW - zivil-militärische Beziehungen KW - Verteidigungspolitik KW - Latin America KW - transition KW - civil-military relations KW - defence policy Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-48231 ER - TY - THES A1 - Mangelsdorf, Stefan T1 - Die Transformation des Verarbeitenden Gewerbes in Berlin/Brandenburg unter Berücksichtigung der Exporte : eine empirische Analyse mit amtlichen Mikrodaten T1 - The transition of the manufacturing industry in Berlin/Brandenburg paying particular consideration to exports : an empirical analyze with official micro data N2 - 20 Jahre sind mittlerweile vergangen seit die friedliche Protestbewegung zur Abdankung des alten Regimes der Deutschen Demokratischen Republik führte. Im darauf folgenden Jahre kam es zur Wiedervereinigung der beiden deutschen Staaten. Der anschließende Transformationsprozess ist aufgrund der besonderen Umstände in Deutschland einzigartig unter den ehemaligen sozialistischen Staaten Mittel- und Osteuropas. Der Schwerpunkt dieser Arbeit liegt in der Transformation des Verarbeitenden Gewerbes in den Bundesländern Berlin und Brandenburg. Mit der Wiedervereinigung der beiden deutschen Staaten veränderte sich die Situation für die Betriebe im ehemals sozialistischen Teil auf dramatische Weise. Die Auswirkungen werden anhand von Makro- und Mikrodaten analysiert. Untersuchungsgegenstände sind verschiedene ökonomische Indikatoren, wie Zahl von Betrieben und Arbeitsplätzen, Strukturen (nach Größe und Branchen), Umsätze (im In- und Ausland) sowie Investitionen. Der Vergleich von Brandenburg und Ostberlin mit Westberlin bietet dabei die Möglichkeit, Aufschluss über den erreichten Stand des Transformationsprozesses zu erhalten. Die Datenbasis dieser Arbeit besteht neben Angaben aus der Volkswirtschaftlichen Gesamtrechnung der Länder aus verschiedenen betriebsbasierten Erhebungen der amtlichen Statistik. Der Beobachtungszeitraum umfasst dabei die Jahre 1991 bis 2005. Zur Analyse von Betriebs- und Beschäftigungszahlen und ihrer Dynamik steht sogar eine Totalerhebung für die Jahre 1991 bis 2000 zur Verfügung. Ein besonderer Schwerpunkt dieser Arbeit ist die Rolle der Exporte für die betriebliche Entwicklung. Die deutsche Wirtschaftspolitik fördert Unternehmen bei ihrem Schritt auf ausländische Märkte, da man sich von Exporten eine Wachstumsstimulation erhofft. Damit eine solche Förderung auch langfristige positive Effekte entfalten kann, muss einerseits der Export positiven Einfluss auf das Produktivitätswachstum des betreffenden Betriebes haben, und andererseits muss das Exportverhalten eine gewisse Persistenz aufweisen. Beide Bedingungen werden innerhalb der Arbeit detailliert untersucht. N2 - 20 years have elapsed since the peaceful protest movement led to the resignation of the old regime in the German Democratic Republic. In the following year both German states reunited. Due to the special situation in Germany the subsequent transformation process is unique within the former socialistic countries of Central and Eastern Europe. The special focus of this thesis is the transition of the manufacturing industry in the federal states of Berlin and Brandenburg. After reunification of the two German states the situation of plants in the former socialistic part changed dramatically. The results are analyzed using, both, macro and micro data. The evolution of some economic indicators, like number of plants and jobs, structure (size and sector), sales (domestic and foreign), and investments, is analyzed. The comparison of Brandenburg and East Berlin with West Berlin provides information about the current state in the transition process. The data used in this study is drawn from two sources: firstly, aggregated data from the national accounts of the federal states, and secondly, micro data from plant based surveys conducted by the official statistics. The observation period covers the years between 1991 and 2005. For the analysis of the number of plants and jobs, and the dynamic in their evolution there could be used a full survey for the years from 1991 to 2000. The thesis pays special attention to the role of exports for the development of plants. German economic policy promotes firms in their step on foreign markets, because exports are expected to stimulate the economic growth. In order that such a promotion has a positive effect in the long run, exports have to have a positive effect on productivity growth, and additionally export behavior has to be persistent over time. Both conditions are empirically examined within this thesis. KW - Transformation KW - Verarbeitendes Gewerbe KW - Exporte KW - Produktivität KW - transition KW - manufacturing KW - exports KW - productivity Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-44414 SN - 978-3-86956-068-7 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Becker, Michael A1 - Neumann, Marko A1 - Tetzner, Julia A1 - Böse, Susanne A1 - Knoppick, Henrike A1 - Maaz, Kai A1 - Baumert, Jürgen A1 - Lehmann, Rainer T1 - Development? Effects of the transition into academically selective schools JF - The journal of educational psychology N2 - The present study investigates school context effects on psychosocial characteristics (academic self-concept, peer relations, school satisfaction, and school anxiety) of high-achieving and gifted students. Students who did or did not make an early transition from elementary to secondary schools for high-achieving and gifted students in 5th grade in Berlin, Germany, are compared in their psychosocial development. The sample comprises 155 early-entry students who moved to an academically selective secondary school (Gymnasium) and 3,169 regular students who remained in elementary school until the end of 6th grade. Overall, a complex pattern of psychosocial development emerged for all students, with both positive and negative outcomes being observed. Specifically, the transition into academically selective learning environments seemed to come at some cost for psychosocial development. Propensity score matching analysis isolating the effects of selective school intake and the school context effect itself revealed negative contextual effects of early transition to Gymnasium on academic self-concept and school anxiety; additionally, the positive trend in peer relations observed among regular students was not discernible among early-entry students. KW - psychosocial development KW - transition KW - ability grouping KW - longitudinal design KW - propensity score matching Y1 - 2014 U6 - https://doi.org/10.1037/a0035425 SN - 0022-0663 SN - 1939-2176 VL - 106 IS - 2 SP - 555 EP - 568 PB - American Psychological Association CY - Washington ER - TY - GEN A1 - Wirth, Jonas A1 - Neumann, Rainer A1 - Antonietti, Markus A1 - Saalfrank, Peter T1 - Adsorption and photocatalytic splitting of water on graphitic carbon nitride BT - a combined first principles and semiempirical study N2 - Graphitic carbon nitride, g-C₃N₄, is a promising organic photo-catalyst for a variety of redox reactions. In order to improve its efficiency in a systematic manner, however, a fundamental understanding of the microscopic interaction between catalyst, reactants and products is crucial. Here we present a systematic study of water adsorption on g-C₃N₄ by means of density functional theory and the density functional based tight-binding method as a prerequisite for understanding photocatalytic water splitting. We then analyze this prototypical redox reaction on the basis of a thermodynamic model providing an estimate of the overpotential for both water oxidation and H⁺ reduction. While the latter is found to occur readily upon irradiation with visible light, we derive a prohibitive overpotential of 1.56 eV for the water oxidation half reaction, comparing well with the experimental finding that in contrast to H₂ production O₂ evolution is only possible in the presence of oxidation cocatalysts. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 172 KW - augmented-wave method KW - hydrogen KW - initio molecular-dynamics KW - oxidation KW - photooxidation KW - reduction KW - simulations KW - tight-binding KW - transition KW - visible-light Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74391 SP - 15917 EP - 15926 ER - TY - JOUR A1 - Wirth, Jonas A1 - Neumann, Rainer A1 - Antonietti, Markus A1 - Saalfrank, Peter T1 - Adsorption and photocatalytic splitting of water on graphitic carbon nitride BT - a combined first principles and semiempirical study JF - physical chemistry, chemical physics : PCCP N2 - Graphitic carbon nitride, g-C₃N₄, is a promising organic photo-catalyst for a variety of redox reactions. In order to improve its efficiency in a systematic manner, however, a fundamental understanding of the microscopic interaction between catalyst, reactants and products is crucial. Here we present a systematic study of water adsorption on g-C₃N₄ by means of density functional theory and the density functional based tight-binding method as a prerequisite for understanding photocatalytic water splitting. We then analyze this prototypical redox reaction on the basis of a thermodynamic model providing an estimate of the overpotential for both water oxidation and H⁺ reduction. While the latter is found to occur readily upon irradiation with visible light, we derive a prohibitive overpotential of 1.56 eV for the water oxidation half reaction, comparing well with the experimental finding that in contrast to H₂ production O₂ evolution is only possible in the presence of oxidation cocatalysts. KW - initio molecular-dynamics KW - augmented-wave method KW - visible-light KW - tight-binding KW - transition KW - oxidation KW - photooxidation KW - simulations KW - reduction KW - hydrogen Y1 - 2014 U6 - https://doi.org/10.1039/c4cp02021a SN - 1463-9076 SN - 1463-9084 VL - 2014 IS - 16 SP - 15917 EP - 15926 ER - TY - JOUR A1 - Banerjee, Pallavi A1 - Lipowsky, Reinhard A1 - Santer, Mark T1 - Coarse-grained molecular model for the Glycosylphosphatidylinositol anchor with and without protein JF - Journal of Chemical Theory and Computation N2 - Glycosylphosphatidylinositol (GPI) anchors are a unique class of complex glycolipids that anchor a great variety of proteins to the extracellular leaflet of plasma membranes of eukaryotic cells. These anchors can exist either with or without an attached protein called GPI-anchored protein (GPI-AP) both in vitro and in vivo. Although GPIs are known to participate in a broad range of cellular functions, it is to a large extent unknown how these are related to GPI structure and composition. Their conformational flexibility and microheterogeneity make it difficult to study them experimentally. Simplified atomistic models are amenable to all-atom computer simulations in small lipid bilayer patches but not suitable for studying their partitioning and trafficking in complex and heterogeneous membranes. Here, we present a coarse-grained model of the GPI anchor constructed with a modified version of the MARTINI force field that is suited for modeling carbohydrates, proteins, and lipids in an aqueous environment using MARTINI's polarizable water. The nonbonded interactions for sugars were reparametrized by calculating their partitioning free energies between polar and apolar phases. In addition, sugar-sugar interactions were optimized by adjusting the second virial coefficients of osmotic pressures for solutions of glucose, sucrose, and trehalose to match with experimental data. With respect to the conformational dynamics of GPI-anchored green fluorescent protein, the accessible time scales are now at least an order of magnitude larger than for the all-atom system. This is particularly important for fine-tuning the mutual interactions of lipids, carbohydrates, and amino acids when comparing to experimental results. We discuss the prospective use of the coarse-grained GPI model for studying protein-sorting and trafficking in membrane models. KW - Martini force-field KW - osmotic-pressure KW - potential-functions KW - aqueous-solution KW - dynamics KW - coefficient KW - simulation KW - trypanosoma KW - transition KW - parameters Y1 - 2020 U6 - https://doi.org/10.1021/acs.jctc.0c00056 SN - 1549-9626 SN - 1549-9618 VL - 16 IS - 6 PB - ACS Publications CY - Washington DC ER - TY - GEN A1 - Banerjee, Pallavi A1 - Lipowsky, Reinhard A1 - Santer, Mark T1 - Coarse-grained molecular model for the Glycosylphosphatidylinositol anchor with and without protein T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Glycosylphosphatidylinositol (GPI) anchors are a unique class of complex glycolipids that anchor a great variety of proteins to the extracellular leaflet of plasma membranes of eukaryotic cells. These anchors can exist either with or without an attached protein called GPI-anchored protein (GPI-AP) both in vitro and in vivo. Although GPIs are known to participate in a broad range of cellular functions, it is to a large extent unknown how these are related to GPI structure and composition. Their conformational flexibility and microheterogeneity make it difficult to study them experimentally. Simplified atomistic models are amenable to all-atom computer simulations in small lipid bilayer patches but not suitable for studying their partitioning and trafficking in complex and heterogeneous membranes. Here, we present a coarse-grained model of the GPI anchor constructed with a modified version of the MARTINI force field that is suited for modeling carbohydrates, proteins, and lipids in an aqueous environment using MARTINI's polarizable water. The nonbonded interactions for sugars were reparametrized by calculating their partitioning free energies between polar and apolar phases. In addition, sugar-sugar interactions were optimized by adjusting the second virial coefficients of osmotic pressures for solutions of glucose, sucrose, and trehalose to match with experimental data. With respect to the conformational dynamics of GPI-anchored green fluorescent protein, the accessible time scales are now at least an order of magnitude larger than for the all-atom system. This is particularly important for fine-tuning the mutual interactions of lipids, carbohydrates, and amino acids when comparing to experimental results. We discuss the prospective use of the coarse-grained GPI model for studying protein-sorting and trafficking in membrane models. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1216 KW - Martini force-field KW - osmotic-pressure KW - potential-functions KW - aqueous-solution KW - dynamics KW - coefficient KW - simulation KW - trypanosoma KW - transition KW - parameters Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-523742 SN - 1866-8372 IS - 6 ER - TY - JOUR A1 - Schifferle, Lukas A1 - Lobanov, Sergey S. T1 - Evolution of chemical bonding and spin-pairing energy in ferropericlase across Its spin transition JF - ACS Earth and Space Chemistry N2 - The evolution of chemical bonding in ferropericlase, (Mg,Fe)O, with pressure may affect the physical and chemical properties of the Earth's lower mantle. Here, we report high-pressure optical absorption spectra of single-crystalline ferropericlase ((Mg0.87Fe0.13)O) up to 135 GPa. Combined with a re-evaluation of published partial fluorescence yield X-ray absorption spectroscopy data, we show that the covalency of the Fe-O bond increases with pressure, but the iron spin transition at 57-76.5 GPa reverses this trend. The qualitative crossover in chemical bonding suggests that the spin-pairing transition weakens the Fe-O bond in ferropericlase. We find, that the spin transition in ferropericlase is caused by both the increase of the ligand field-splitting energy and the decrease in the spin-pairing energy of high-spin Fe2+. KW - high-pressure KW - diamond anvil cell KW - covalency KW - bond strength KW - iron KW - spin KW - transition Y1 - 2022 U6 - https://doi.org/10.1021/acsearthspacechem.2c00014 SN - 2472-3452 VL - 6 IS - 3 SP - 788 EP - 799 PB - American Chemical Society CY - Washington ER -