The Jahn-Teller Effect

No abstract is available for this article.

The availability of quantitatively accurate total energies $({E}_{\mathrm{tot}})$ of atoms, molecules, and solids, enabled by the development of density functional theory (DFT), has transformed solid state physics, quantum chemistry, and materials science by allowing direct calculations of measureable quantities, such as enthalpies of formation $(\mathrm{\ensuremath{\Delta}}{H}_{f})$. Still, the ability to compute ${E}_{\mathrm{tot}}$ and $\mathrm{\ensuremath{\Delta}}{H}_{f}$ values does not, necessarily, provide insights into the physical mechanisms behind their magnitudes or chemical trends. Here, we examine a large set of calculated ${E}_{\mathrm{tot}}$ and $\mathrm{\ensuremath{\Delta}}{H}_{f}$ values obtained from the DFT+$U$-based fitted elemental-phase reference energies (FERE) approach [V. Stevanovi\ifmmode \acute{c}\else \'{c}\fi{}, S. Lany, X. Zhang, and A. Zunger, Phys. Rev. B 85, 115104 (2012)] to probe relationships between the ${E}_{\mathrm{tot}}/\mathrm{\ensuremath{\Delta}}{H}_{f}$ of metal-nonmetal compounds in their ground-state crystal structures and properties describing the compound compositions and their elemental constituents. From a stepwise linear regression, we develop a linear model for ${E}_{\mathrm{tot}}$, and consequently $\mathrm{\ensuremath{\Delta}}{H}_{f}$, that reproduces calculated FERE values with a mean absolute error of \ensuremath{\sim}80 meV/atom. The most significant contributions to the model include calculated total energies of the constituent elements in their reference phases (e.g., metallic iron or gas phase ${\mathrm{O}}_{2}$), atomic ionization energies and electron affinities, Pauling electronegativity differences, and atomic electric polarizabilities. These contributions are discussed in the context of their connection to the underlying physics. We also demonstrate that our ${E}_{\mathrm{tot}}/\mathrm{\ensuremath{\Delta}}{H}_{f}$ model can be directly extended to predict the ${E}_{\mathrm{tot}}$ and $\mathrm{\ensuremath{\Delta}}{H}_{f}$ of compounds outside the set used to develop the model.

With the advent of new high-power, short-pulse laser facilities in combination with novel technologies for the production of highly brilliant, intense γ beams (like, e.g., Extreme Light Infrastructure – Nuclear Physics (ELI-NP) in Bucharest, MEGaRay in Livermore or a planned upgrade of the HIγS facility at Duke University), unprecedented perspectives will open up in the coming years for photonuclear physics both in basic sciences as in various fields of applications. Ultra-high sensitivity will be enabled by an envisaged increase of the γ-beam spectral density from the presently typical 102γ/eVs to about 104γ/eVs, thus enabling a new quality of nuclear photonics [1], assisted by new γ-optical elements [2]. Photonuclear reactions with highly brilliant γ beams will allow to produce radioisotopes for nuclear medicine with much higher specific activity and/or more economically than with conventional methods. This will open the door for completely new clinical applications of radioisotopes [3]. The isotopic, state-selective sensitivity of the well-established technique of nuclear resonance fluorescence (NRF) will be boosted by the drastically reduced energy bandwidth (<0.1%) of the novel γ beams. Together with a much higher intensity of these beams, this will pave the road towards a γ-beam based non-invasive tomography and microscopy, assisting the management of nuclear materials, such as radioactive waste management, the detection of nuclear fissile material in the recycling process or the detection of clandestine fissile materials. Moreover, also secondary sources like low-energy, pulsed, polarized neutron beams of high intensity and high brilliance [4] or a new type of positron source with significantly increased brilliance, for the first time fully polarized [5], can be realized and lead to new applications in solid state physics or material sciences.

The Jahn-Teller effect is a fascinating and ubiquitous phenomenon in modern quantum physics and chemistry. We propose a class of oxides with melilite structure Ba$_2$TGe$_2$O$_7$ (T=V,Ni) where Jahn-Teller distortions are the main responsibles for the appearance of electric polarization. At the hearth of the proposed mechanism lies the lack of inversion symmetry displayed by tetrahedrally coordinated transition-metal ions, which allows for the condensation of polar Jahn-Teller distortions, at odds with octahedral coordination typical of conventional ferroelectric oxides with perovskite structure. Since the noncentrosymmetric local environment of transition-metal ions also activates the proposed spin-dependent hybridization mechanism for magnetically-induced electric polarization, proper multiferroic phases with intrinsic magnetoelectric interaction could be realized in this class of low-symmetry materials.

The 12th National Conference on Solid State Physics and Materials Science (SPMS2021) gathered various notable scientists (7 plenary speakers and 34 invited speakers). Attending the conference and actively participating in the debate were more than 450 scholars with an interest in the topic. Four hundred reports were divided into five specialized sessions, including (A) physics and magnetic materials, (B) semiconductor and dielectric physics, (C) semiconductor and dielectric materials and devices, (D) biomedical materials and materials for agriculture, energy, and the environment, and (E) composite materials - metals, ceramics, and Vietnam-Korea sessions on applied physics. In addition, the Organizing Committee received numerous full-text reports that had been submitted to the Journal of Science and Technology (Vietnam Academy of Science and Technology) following a rigorous review procedure. SPMS2021 co-organized by the Vietnam Physical Society, the Vietnam Materials Research Society (V-MRS), the Institute of Physics, the Institute of Materials Science (Vietnam Academy of Science and Technology), Hanoi University of Science and Technology, Vietnam National University (VNU), Phenikaa University, and Can Tho University was held on 13 – 15 August 2022 in Can Tho City after nearly 9 months of postponement due to the COVID-19 pandemic. The conference has attracted 7 plenary speakers, 34 invited speakers, and over 450 scientists (Figure 1, Table 1, and Table 2) 1. It is not only a sizable and esteemed scientific conference that draws the interest of the Vietnamese scientific community, but it is also a venue for getting together, exchanging ideas, and disseminating the most recent advancements in the SPMS sector. Since 1995, it has been conducted continuously every two years. Many scientists are generally interested in the domains of solid-state physics and materials science, which have a wide range of activities and exceptional accomplishments in both basics and applications in Vietnam.

We review recent developments in atomistic computer simulations of matter incorporating both quantum and classical statistical mechanical elements. These methods treat the electronic and geometric structure of solids, liquids and molecules on an equal footing and require no a priori knowledge (i.e. they are based on “first principles”, the basic laws of quantum and classical physics, not on experimental information). They borrow elements from quantum chemistry and solid state electron theories on one side and classical mechanics on the other. Such unified approach leads to more reliable computer-based predictions of materials properties over traditional simulation methods but requires substantial supercomputing resources. We present two typical applications in chemistry (nanoscale clusters of the element phosphorus) and solid state physics (the element hydrogen at extremely high compression).

pss Rapid Research Letters – the fastest peer‐reviewed publication medium in solid state physics

Light. Volume 2. Laser Light Dynamics. By H. Haken. (Amsterdam, New York, Oxford: North-Holland, 1985.) [Pp. xxiii + 336 + subject index.] Price Dfl. 125·00/US $46.25 hard cover. Electronic Structure and Electronic Transitions in Layered Materials. Edited by V. Grasso. (Dordrecht, Boston, Lancaster: D. Reidel, 1986.) [Pp. ix + 491 + author and subject index.] Price Dfl.225.00 hard cover. The Physics and Fabrication of Microstructures and Microdevices. Edited by M. J. Kelly and C. Weisbuch. (Berlin, Heidelberg, New York: Springer-Verlag, 1986.) [Pp. xi + 460.1 Price DM 99·00 hard cover. Unitary Transformations in Solid State Physics. By M. Wagner. (Amsterdam, Oxford, New York: North-Holland, 1986.) [Pp. xvi + 341 + author and subject index.] Price Dfl.225.00 hard cover. Differential Manifolds and Theoretical Physics. By W. D. Curtis and F. R. Miller. (Orlando, San Diego and New York: Academic Press, 1985.) [Pp. xiii + 388 + subject index.] Price £69·00 hard cover. Coherent States. Applications in Physics and Mathematical Physics. By J. R. Klauder and B. Skagerstam. (Singapore: World Scientific, 1985.) [Pp. xvii + 911.] Price £6670 soft cover. (69 reprints from various journals + introduction.) International Tables for Crystallography. Edited by T. Hahn. (Dordrecht, Boston, Lancaster: D. Reidel, 1985.) [Pp. viii +119.1 Price £9·00 soft cover. (Brief Teaching Edition of Volume A—Space-Group Symmetry.) Multiple Time Scales. Edited by J. U. Brackbill and B. I. Cohen. (Orlando, San Diego, New York: Academic Press, 1985.) [Pp. xiii + 436 + subject index.] Price ·65.00 hard cover. (Thirteen reviews of applications in physics.) Silicon-on-Insulator: Its Technology and Applications. Edited by S. Furukawa. (Dordrecht, Boston, London: D. Reidel; and Tokyo: KTK Scientific Publishers, 1985.) [Pp. vii + 295 + author index.] Price £49·95 hard cover. (20 papers presented at the seminar on ‘Solid Phase Epitaxy and Interface Kinetics’ held in Oiso, Japan, June, 1983.) Layered Structures and Interface Kinetics: Their Technology and Applications. Edited by S. Furukawa. (Dordrecht, Boston, London: D. Reidel; and Tokyo: KTK Scientific Publishers, 1985.) [Pp. viii + 367 + author index.] Price £60·95 hard cover. (22 papers presented at the seminar on ‘Solid Phase Epitaxy and Interface Kinetics’ held in Oiso, Japan, June, 1983.) Superlattices and Microstructures. Volume 1. Number 1. Edited by J. D. Dow. (Orlando, London, New York: Academic Press, 1985.) [Pp. 96.] soft cover. (New interdisciplinary journal devoted to the physics, chemistry, materials science and electrical engineering of submicron structures not only in semiconductors but also in materials with metallic, insulating and superconducting properties.) Solid Clues. Quantum Physics, Molecular Biology, and the Future of Science. By G. Feinberg. (London: Heinemann, 1985.) [Pp. i + 278 + subject index.] Price £12·95 hard cover. Laser Spectroscopy of Solids. Second Printing. Edited by W. M. Yen and P. M. Selzer. (Berlin, Heidelberg, New York: Springer-Verlag, 1986.) [Pp. xiv + 311 + subject index.] Price DM79 soft cover (See Phil. Mag. B, 44, 185 for review.)

It is with great pleasure that we present this special issue focused on topological structures in ferroic materials. It is composed of invited contributions from the International Workshop on Topological Structures in Ferroic Materials held at the University of South Wales, Sydney, Australia from 19-21 st May 2015. The aim of the workshop was to capture current research interests regarding interfaces, domains, domain walls, vortices and skyrmions in ferroics as an emerging and highly active fi eld in solid state physics and materials science. Signifi cant emphasis was placed on understanding the fundamental commonalities that bridge topological defects across various types of ferroic materials, and therefore lessons learned on how new and groundbreaking functionalities afforded by the aforementioned concepts could be translated into emerging technologies.

The global utilization of nuclear energy has come a long way from its humble beginnings in the first sustained nuclear reaction at the University of Chicago in 1942. Today, there are over 440 nuclear reactors in 31 countries producing approximately 16% of the electrical energy used worldwide. In the United States, 104 nuclear reactors currently provide 19% of electrical energy used nationally. The International Atomic Energy Agency projects significant growth in the utilization of nuclear power over the next several decades due to increasing demand for energy and environmental concerns related to emissions from fossil plants. There are 28 new nuclear plants currently under construction including 10 in China, 8 in India, and 4 in Russia. In the United States, there have been notifications to the Nuclear Regulatory Commission of intentions to apply for combined construction and operating licenses for 27 new units over the next decade. The projected growth in nuclear power has focused increasing attention on issues related to the permanent disposal of nuclear waste, the proliferation of nuclear weapons technologies and materials, and the sustainability of a once-through nuclear fuel cycle. In addition, the effective utilization of nuclear power will require continued improvements in nuclear technology, particularly related to safety and efficiency. In all of these areas, the performance of materials and chemical processes under extreme conditions is a limiting factor. The related basic research challenges represent some of the most demanding tests of our fundamental understanding of materials science and chemistry, and they provide significant opportunities for advancing basic science with broad impacts for nuclear reactor materials, fuels, waste forms, and separations techniques. Of particular importance is the role that new nanoscale characterization and computational tools can play in addressing these challenges. These tools, which include DOE synchrotron X-ray sources, neutron sources, nanoscale science research centers, and supercomputers, offer the opportunity to transform and accelerate the fundamental materials and chemical sciences that underpin technology development for advanced nuclear energy systems. The fundamental challenge is to understand and control chemical and physical phenomena in multi-component systems from femto-seconds to millennia, at temperatures to 1000?C, and for radiation doses to hundreds of displacements per atom (dpa). This is a scientific challenge of enormous proportions, with broad implications in the materials science and chemistry of complex systems. New understanding is required for microstructural evolution and phase stability under relevant chemical and physical conditions, chemistry and structural evolution at interfaces, chemical behavior of actinide and fission-product solutions, and nuclear and thermomechanical phenomena in fuels and waste forms. First-principles approaches are needed to describe f-electron systems, design molecules for separations, and explain materials failure mechanisms. Nanoscale synthesis and characterization methods are needed to understand and design materials and interfaces with radiation, temperature, and corrosion resistance. Dynamical measurements are required to understand fundamental physical and chemical phenomena. New multiscale approaches are needed to integrate this knowledge into accurate models of relevant phenomena and complex systems across multiple length and time scales.

The joint International Symposium RCBJSF–2014–FM&NT successfully has united two international events – 12th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity (RCBJSF-12) and 9th International Conference Functional Materials and Nanotechnologies (FM&NT-2014). The RCBJSF symposium is a continuation of series of meetings on ferroelectricity, the first of which took place in Novosibirsk (USSR) in 1976. FM&NT conferences started in 2006 and have been organized by Institute of Solid State Physics, University of Latvia in Riga. In 2012 the International program committee decided to transform this conference into a traveling Baltic State conference and the FM&NT-2013 was organized by the Institute of Physics, University of Tartu, Estonia. In 2014 the joint international symposium RCBJSF–2014–FM&NT was organized by the Institute of Solid State Physics, University of Latvia and was part of Riga – 2014, the European Capital of Culture event. The purpose of the joint Symposium was to bring together scientists, students and high-level experts in solid state physics, materials science, engineering and related disciplines. The number of the registered participants from 26 countries was over 350. During the Symposium 128 high quality scientific talks (5 plenary, 42 invited, 81 oral) and over 215 posters were presented. All presentations were divided into 4 parallel sessions according to 4 main topics of the Symposium: Ferroelectricity, including ferroelectrics and multiferroics, pyroelectrics, piezoelectrics and actuators, integrated ferroelectrics, relaxors, phase transitions and critical phenomena. Multifunctional Materials, including theory, multiscale and multiphenomenal material modeling and simulation, advanced inorganic, organic and hybrid materials. Nanotechnologies, including progressive methods, technologies and design for production, investigation of nano- particles, composites, structures, thin films and coatings. Energy, including perspective materials and technologies for renewable and hydrogen energy, fuel cells, photovoltaics, LEDs, OLEDs. Based on these reports, 48 papers are included in this volume of IOP Conference Series: Materials Science and Engineering. Additional information about RCBJSF–2014–FM&NT is available at the homepage http://www.fmnt.lu.lv. The Organizing Committee would like to thank all the speakers, contributors, session chairs, referees and other involved staff for their efforts in making the RCBJSF–2014–FM&NT successful. Sincerely, organizers of the event Andris Sternberg Liga Grinberga Anatolijs Sarakovskis Martins Rutkis

ZnO tetrapod materials for functional applications

In a semi-review paper (a review with novel results included), we note first that the so-called Jahn-Teller effects (JTEs), in their presently recognized four modifications, emerge as particular cases of a more general law, stating that “Nature tends to avoid degeneracies and pseudo-degeneracies in atomic matter by means of spontaneous symmetry breaking (SSB)”. This “Law of Nature” obviously influences all the relevant properties of polyatomic systems, including those with direct applications in materials science and engineering, as well as in materials transformations, notably, in chemical reactions. The exploration to the latter is quite novel: we show that the energy barriers in chemical transformations are controlled by the pseudo-JTE (PJTE), opening uncharted ways of catalytic action. The applications of JTEs theory in materials science is already more advanced, utilizing the SSB-induced special nuclear dynamics, which is very sensitive to external perturbations. One of its novel aspects is to modify the properties of the system by means of external influence targeting its JTEs parameters, their underlying degeneracies. We show here some notable trends with illustrative examples, including the JTEs in local centers in crystals used as qubits in quantum information storage, alteration of whole crystal lattice properties by inducing the JTE in one of its sublattices, planarization of puckered (buckled) two-dimensional systems by coordination to atoms that quench their PJTE-induced out-of-plane distortion, and the origin of a whole series of solid state properties of perovskite crystals, triggered by the local PJTE.

Quasiperiodic and Disordered Interfaces in Nanostructured Materials

Continuous progress in Solid State Physics and Materials Science has developed through a permanent interplay between theory and experiments in which spectroscopy is taking a major part. Absorption and Reflectivity spectroscopy is a key method for determining band gaps, necessary for establishing of electronic band structures and phonon dispersion relations which are the basic characteristics of materials.