The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. It has moved into a central place in condensed matter studies. Statistical physics, and more specifically, the theory of transitions between states of matter, more or less defines what we know about 'everyday' matter and its transformations. The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable information on important recent developments.

Phase Transitions and Critical Phenomena

“…. For the truth of the conclusions of physical science, observation is the supreme Court of Appeal….” (Sir Arthur Eddington, The Philosophy of Physical Science.) In this paper we shall review the theoretical and experimental results obtained on simple magnetic model systems. We shall consider the Heisenberg, XY and Ising type of interaction (ferro and antiferromagnetic), on magnetic lattices of dimensionality 1, 2 and 3. Particular attention will be paid to the approximation of these model systems in real crystals, viz. how they can be realized or be expected to exist in nature. A large number of magnetic compounds which, according to the available experimental information, meet the requirements set by one or the other of the various models are considered and their properties discussed. Many examples will be given that demonstrate to what extent experiments on simple magnetic systems support theoretical descriptions of magnetic ordering phenomena and contribute to their understanding. It will a...

Experiments on simple magnetic model systems

The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c = 26 K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic. In short order, ot...

The puzzle of high temperature superconductivity in layered iron pnictides and chalcogenides

1. Introduction 2. Nuclear scattering - basic theory 3. Nuclear scattering by crystals 4. Correlation functions in nuclear scattering 5. Scattering by liquids 6. Neutron optics 7. Magnetic scattering - basic theory 8. Scattering from magnetically ordered crystals 9. Polarisation analysis Appendices Solutions to examples Index.

https://assets.cambridge.org/97811076/44069/frontmatter/9781107644069_frontmatter.pdf

Introduction to the Theory of Thermal Neutron Scattering

A ubiquitous observation in cell biology is that the diffusive motion of macromolecules and organelles is anomalous, and a description simply based on the conventional diffusion equation with diffusion constants measured in dilute solution fails. This is commonly attributed to macromolecular crowding in the interior of cells and in cellular membranes, summarizing their densely packed and heterogeneous structures. The most familiar phenomenon is a sublinear, power-law increase of the mean-square displacement (MSD) as a function of the lag time, but there are other manifestations like strongly reduced and time-dependent diffusion coefficients, persistent correlations in time, non-Gaussian distributions of spatial displacements, heterogeneous diffusion and a fraction of immobile particles. After a general introduction to the statistical description of slow, anomalous transport, we summarize some widely used theoretical models: Gaussian models like fractional Brownian motion and Langevin equations for visco-elastic media, the continuous-time random walk model, and the Lorentz model describing obstructed transport in a heterogeneous environment. Particular emphasis is put on the spatio-temporal properties of the transport in terms of two-point correlation functions, dynamic scaling behaviour, and how the models are distinguished by their propagators even if the MSDs are identical. Then, we review the theory underlying commonly applied experimental techniques in the presence of anomalous transport like single-particle tracking, fluorescence correlation spectroscopy (FCS) and fluorescence recovery after photobleaching (FRAP). We report on the large body of recent experimental evidence for anomalous transport in crowded biological media: in cyto- and nucleoplasm as well as in cellular membranes, complemented by in vitro experiments where a variety of model systems mimic physiological crowding conditions. Finally, computer simulations are discussed which play an important role in testing the theoretical models and corroborating the experimental findings. The review is completed by a synthesis of the theoretical and experimental progress identifying open questions for future investigation.

https://iopscience.iop.org/article/10.1088/0034-4885/76/4/046602/pdf

Anomalous transport in the crowded world of biological cells.

Theory of neutron scattering from condensed matter

Theory of Thermal Neutron Scattering

The computer simulation and inelastic neutron scattering studies of simple, monatomic liquids are reviewed, together with the theory appropriate for their interpretation. Computer simulation (molecular dynamics) studies influenced development of non-equilibrium statistical mechanics techniques for the calculation of correlation functions that enter the various measured susceptibilities. Studies of systems interacting via continuous potentials have developed to a high level of sophistication. Neutron scattering experiments are difficult to perform with high accuracy, yet offer a unique means of investigating the dynamics of simple liquids in the domain of wavevectors and frequencies larger than about 0.05 AA-1 and 5*1011 s-1 respectively. The problems faced in analysing neutron data to the level required are reviewed in detail. Theory has developed through the rigorous generalization of the Markovian theory of fluctuations set out by Landau and Lifshitz (1959). The development has taken the form of a generalized Langevin equation, which provides a framework within which neutron and molecular dynamics data may be interpreted.

http://iopscience.iop.org/article/10.1088/0034-4885/38/4/001/pdf

The dynamic properties of monatomic liquids

1. Introductory survey 2. Non-resonant magentic X-ray diffraction from antiferromagnets 3. Non-resonant magnetic diffraction from ferromagnets 4. Magnetic X-ray dichroism 5. Resonant X-ray diffraction from antiferromagnets 6. Resonant magnetic X-ray diffraction from ferromagnets 7. Compton scattering 8. Theoretical framework Appendix Index

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X-ray scattering and absorption by magnetic materials

1 Introduction- 11 Prologue- 12 Correlation Functions- 13 Nuclear Scattering- 131 Scattering by Phonons- 132 Phonon Interactions- 133 Electron-Phonon Interactions- 134 Monoatomic Liquids- 135 Molecular Gases- 14 Polarization Effects- 15 Magnetic Scattering- 151 Ferromagnetic Spin Waves- 152 Antiferromagnetic Spin Waves- 153 Paramagnetic Scattering- Appendix A: Crystal Lattices and Reciprocal Lattices- References- 2 Phonons- 21 Lattice Dynamics and Neutron Scattering- 211 General Model- 212 Rigid-Ion and Shell Models- 213 Experimental- 22 Lattice Dynamics of Crystals of the Rutile Type - TiO2, MgF2, and MnF2- 221 TiO2- 222 MgF2- 223 MnF2- 224 Conclusions- 23 Phonon Anomalies in Superconducting Materials- 231 Transition Metal Carbides- 232 A-15 Compounds- 233 Niobium-Alloys, Other Compounds, and Impurities- 234 Other Superconductors - Tc, Mo-Re, Hg- 235 Conclusions- 24 Layered Compounds- 241 MoS2- 242 NbSe2- 243 Graphite- 244 PbI2- 245 Concluding Remarks- 25 Effects of Pressure on Phonon Spectra- 251 Experimental Aspects- 252 Phonon Shifts and Widths in Neon- 253 Selected Phonons in Rubidium as a Function of Temperature and Volume- 254 Conclusions- References- 3 Phonons and Structural Phase Transformations- 31 Relation Between Neutron and X-Ray Scattering Techniques- 311 Elastic and Inelastic Scattering- 312 Experimental Technique- Inelastic Neutron Scattering- X-Ray Scattering- 313 Correlations and Dimensionality in Real and Reciprocal Space- 32 Fluctuations and Order- 321 Soft Modes- 322 Critical Slowing Down- 323 Eigenvector and Order Parameter- 33 Experimental Results- 331 Ferrodistortive Transformations- 332 Antiferrodistortive Transformations- 333 Modulated Lattices and Low Dimensional Systems- References- 4 Dynamics of Molecular Crystals, Polymers, and Adsorbed Species- 41 Molecular Crystals- 411 Models for the Lattice Dynamics in Molecular Crystals- 412 The Lattice Dynamics of ?-Paradichlorobenzene- 413 The Dynamics of Hexamethylenetetramine- 414 Incoherent Neutron Scattering, Phonon Density of States, and Intramolecular Vibrations- 415 Molecular Torsional Motions and Tunneling Spectroscopy- 416 Phonon Density of States Measurements by Optical Spectroscopy- 42 Polymers- 421 Polyethylene - the Isolated Chain and Incoherent Scattering Studies- 422 Polyoxymethylene- 423 Biopolymers- 43 Structure and Dynamics of Adsorbed Species- 431 Substrates- 432 Physisorption- 433 Incoherent Scattering- 44 Chemisorption- 441 Hydrocarbons Adsorbed on Zeolites- 442 Hydrogen Adsorbed on Metals- 45 Intercalation Compounds- 451 Tantalum Disulphide-Ammonia- 452 Translational Diffusion in Alumino-Silicate Minerals- 46 Conclusions- References- 5 Molecular Rotations, and Diffusion in Solids, in Particular Hydrogen in Metals- 51 Diffusion in Solids, in Particular Hydrogen in Metals- 511 General Aspects- 512 Experiments on Hydrogen in Pd, a fcc-Lattice- 513 Hydrogen in the bcc Metals Ta, Nb, and V- 514 The Temperature- and Q-Dependence of the Quasielastic Intensity- 515 Conclusions on H-Metal Systems Other Problems of Diffusion in Solids- 52 Rotations in Molecular Solids- 521 Rotations and Hindrance Potential Scattering Law- 522 High Temperatures: Rotational Jumps and Rotational Diffusion- 523 Fixed-Window-Method- 524 Low Temperature Experiments Quantum Rotations- 53 Liquids, Liquid Crystals, and Related Problems- 531 The Scattering Law for Molecular Liquids- 532 Liquid Crystals, Polymers- References- 6 Collective Modes in Classical Monoatomic Liquids- 61 Collective Modes- 611 Collective Variables- 612 Generalized Hydrodynamics- 62 Coherent Scattering- 621 Insulating Liquids- 622 Liquid Metals- 623 Comparison of Systems Studied- 63 Transverse Current Correlations- 64 Relations Between S(Q,?) and Ss(Q,?)- 65 Current Issues- References- 7 Magnetic Scattering- 71 Magnons in Ionic Compounds- 72 Quasi One- and Two-Dimensional Systems- 721 Magnetic Linear-Chain Systems- 722 Layered Magnetic Systems- 73 Magnons in Metals- 74 Crystal Field Levels in Rare Earth Compounds- 75 Magnons and Excitons in Rare Earth Metals- 76 Critical Magnetic Scattering- 77 Hyperfine Field Measurements- References

Stephen W. Lovesey

Papers

Theory of neutron scattering from condensed matter

Theory of Thermal Neutron Scattering

The dynamic properties of monatomic liquids

X-ray scattering and absorption by magnetic materials

Dynamics of solids and liquids by neutron scattering