We present a model equation of states for expanded metals, which contains a pressure term due to a screened-Coulomb potential with a screening parameter reflecting the Mott-Anderson metal-to-nonmetal transition. As anticipated almost 80 years ago by Zel'dovich and Landau, this term gives rise to a second coexistence line in the phase diagram, indicating a phase separation between a metallic and a nonmetallic liquid.

The small-angle X-ray scattering data of expanded fluid mercury published in the literature were evaluated using a modified form of the Teubner-Strey equation for microemulsions together with the general treatment of two-phase systems according to Porod. The parameters obtained in the critical region and the metal-nonmetal (M-NM) transition are evidence of a nanoemulsion composed of M and NM domains. The structure of this emulsion is characterized by density, volume fraction and size parameters (average chord length, polydispersity) of the domains. On the basis of these parameters, a structural model for fluid mercury in the liquid-vapour critical region and the M-NM transition is developed. Analysis of the relationship between the volume fraction of the M domains and the electrical conductivity reveals that a percolation transition occurs, with a threshold located near the liquid-vapour critical density. This observation is consistent with recent theoretical developments.

In a letter to one of the authors, Sir Nevill Mott, then in his tenth decade, highlighted the fact that the statement '... a metal conducts, and a non-metal doesn't' can be true only at the absolute zero of temperature, T=0 K. But, of course, experimental studies of metals, non-metals and, indeed, the electronic and thermodynamic transition between these canonical states of matter must always occur above T=0 K, and, in many important cases, for temperatures far above the absolute zero. Here, we review the issues-theoretical and experimental-attendant on studies of the metal to non-metal transition in doped semiconductors at temperatures close to absolute zero (T=0.03 K) and fluid chemical elements at temperatures far above absolute zero (T>1000 K). We attempt to illustrate Mott's insights for delving into such complex phenomena and experimental systems, finding intuitively the dominant features of the science, and developing a coherent picture of the different competing electronic processes. A particular emphasis is placed on the idea of a 'Mott metal to non-metal transition' in the nominally metallic chemical elements rubidium, caesium and mercury, and the converse metallization transition in the nominally non-metal elements hydrogen and oxygen. We also review major innovations by D. A. Goldhammer (Goldhammer 1913 Dispersion und absorption des lichtes) and K. F. Herzfeld (Herzfeld 1927 Phys. Rev. 29, 701-705. (doi:10.1103/PhysRev.29.701)) in a pre-quantum theory description of the metal-non-metal transition, which emphasize the pivotal role of atomic properties in dictating the metallic or non-metallic status of the chemical elements of the periodic table under ambient and extreme conditions; a link with Pauling's 'metallic orbital' is also established here.

We have performed quantum molecular dynamics simulations for expanded fluid Rb and Cs. We compare the pair correlation functions with results derived from neutron and x-ray scattering experiments. The experimentally observed structural changes with the density and temperature variation are reproduced. The density of states and the electronic charge density extracted from the simulations indicate a crossover from metallic to nonmetallic behaviour near the critical point due to a localization of electrons at nuclei.

Selected experimental results are reported of the temperature dependence of the real part of the dielectric constant ε1 of sub- and supercritical mercury vapour relatively close to the critical point. The functional form of the temperature dependence of ε1 along isochores close to the critical isochore has a cusp-like anomaly near the critical temperature. The anomalous increase in ε1 reaches about 70% for mercury at densities very close to the critical density.

Angewandte ChemieVolume 117, Issue 8 p. 1180-1180 Nachruf Ernst-Ulrich Franck (1920–2004): Fluide bei hohen Drücken und überkritischen Temperaturen Friedrich Hensel, Friedrich Hensel MarburgSearch for more papers by this author Friedrich Hensel, Friedrich Hensel MarburgSearch for more papers by this author First published: 04 February 2005 https://doi.org/10.1002/ange.200500097Citations: 3Read the full textAboutPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume117, Issue8February 11, 2005Pages 1180-1180 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. RelatedInformation

Over the past forty years, the application of high pressures has proven to be a powerful and nearly indispensable tool in chemistry, physics, geology, and biology research. Ever-increasing sophistication in experimental high-pressure techniques coupled with new theoretical developments have resulted in important advances in the understanding of the molecular structures, electronic properties, dynamics, and reactivity of condensed matter. One of the towering pioneers of this development was Harry G. Drickamer (Figure 1), Professor of Chemical Engineering, Chemistry and Physics at the University of Illinois in Urbana-Champaign, who died of a stroke on May 6, 2002 in Urbana, Illinois, at the age of 83. Harry G. Drickamer (Copyright Dept. Chemical Engineering, University of Illinois, Urbana, IL, USA). Harry Drickamer was born on November 19, 1918 in Cleveland, Ohio. After graduating from high school he attended Indiana University for a short period. He then transferred to the University of Michigan, where he received his bachelor's degree in 1941, his master's degree in chemical engineering in 1942, and his doctorate in chemical engineering in 1946. That same year he joined the University of Illinois in Urbana-Champaign, where he was appointed, in recognition of the breadth of his research, Center of Advanced Study Professor of Chemical Engineering, Chemistry, and Physics, the highest accolade bestowed by the University on its faculty members. During his more than 50 years of research in Urbana, he developed the concept that pressure can change the chemical and physical properties of condensed matter by its effect on the electronic orbitals, a method he called “Pressure Tuning Spectroscopy”. Exploitation of this method led to his discovery in the late 1950s of a wide variety of electronic transitions in solids, including insulator–metal transitions for six elements and more than 30 covalent and ionic compounds, metal–semiconductor transitions for the elements calcium, strontium, and ytterbium, (which are metals at one atmosphere and which become semiconductors at high pressure), and s–d or 4f–5d transitions of the conducting electrons in alkali and rare-earth metals, respectively. In the 1970s he also investigated closely related pressure-induced changes to magnetic properties, such as high-spin–low-spin transitions and paramagnetic–ferromagnetic transitions in ferrous compounds and in iron. Furthermore, he discovered electronic transitions with chemical consequences, such as the stabilization of reactive charge-transfer states of electron donor–acceptor complexes at high pressures and the pressure-induced conversion of photochromic into thermochromic materials. In the 1980s his research expanded to high-pressure investigations in protein chemistry, organic photochemistry, and the efficiency of luminescence devices. Harry Drickamer's style of experimental research kept him in close contact with theoretical work. In this way, he was able to provide clear-cut and unequivocal tests for a large number of theories, including the ligand-field theory, van Vleck's theory of spin-flip transitions, Mulliken's theory of bonding in electron donor–acceptor complexes, the Förster–Dexter theory of energy transfer in phosphors, and van Vleck's theory of high-spin–low-spin transitions. He also developed successful tests for theories on the efficiency of phosphor and laser materials, including II-VI and III-V compounds with zinc-blende structure, rare-earth oxides, chelates, and organic phosphors. The list of his awards and honors is too long to relate in full, and reflects not only universal respect and admiration for his scientific research, but also the remarkable breadth of his activities. The 27 awards he received were for both research and teaching, and were from organizations in physics, chemistry, and chemical engineering. Among them were the Oliver E. Buckley Prize in Condensed Matter Physics from the American Physical Society (1967), the Irving Langmuir Award in Chemical Physics (1974), the Peter Debeye Award of the American Chemical Society (1987), the first P. W. Bridgman Award of the International Association for the Advancement of High-Pressure Science and Technology (1977), and a Research Award from the Alexander von Humboldt Foundation of the Federal Republic of Germany (1986). In 1989, President George H. W. Bush awarded him the National Medal of Science. Drickamer's laboratory in Urbana attracted scientists and students from many places around the world. His passionate interest in high-pressure research continued after his retirement in 1989. Even then, he did not change his research schedule, but continued to maintain an active and successful research group and was in the laboratory six days a week. The results of 56 years of high-pressure research were published in more than 450 original contributions to the scientific literature. A summary, in Drickamer's own words, of the impact of “Pressure Tuning Spectroscopy”, can be found in Annual Reviews Materials Science 1990, 1–17. Insight into his research can be found in his review on “Electronic Transitions in Transition Metal Compounds at High Pressure” (Angew. Chem. 1974, 86, 61–79; Angew. Chem. Int. Ed. Engl. 1974, 13, 39–47). Dickamer's scientific work has affected high-pressure research in an important way and will continue to do so in the future. Those who have been fortunate and privileged enough to work with him as students, colleagues, or friends owe him a great debt of gratitude. We will miss him.

Short-wavelength collective excitations in liquid mercury at room temperature have been studied by inelastic X-ray scattering. Up to Q values of about 17 nm-1, clear evidence for the existence of propagating modes was found from the shape of S(Q,ω) at constant Q. The Q–ω behaviour of these excitations is described in a simplified viscoelastic view.

Short wavelength collective excitations in liquid Hg at room temperature have been investigated by high-resolution inelastic X-ray scattering. Clear evidence for the existence of propagating modes was found from the S(Q,ω) at constant Q up to about 17 nm−1. A positive dispersion in the Q–ω relation for these excitations was identified. This behavior is described in a simplified viscoelastic view.

We present the first results for the dynamic structure factor S(Q,omega) of liquid Ge at 980 degreesC obtained from inelastic x-ray scattering experiments. Distinct exitations resulting from propagating modes can be identified. The phonon dispersion obtained in the present experiments matches the hydrodynamic sound velocity in the low Q range, i.e., no positive dispersion can be detected. This result is, however, inconsistent with generalized hydrodynamics beyond Q = 5 nm(-1).

Scalar relativistic coupled cluster calculations for the potential energy curve and the distance dependence of the static dipole polarizability tensor of Hg2 are presented and compared with current experimental work. The role of the basis set superposition error for the potential energy curve and the dipole polarizability is discussed in detail. Our recently optimized correlation consistent valence basis sets together with energy adjusted pseudopotentials are well suited to accurately describe the van der Waals system Hg2. The vibrational–rotational analysis of the best spin–orbit corrected potential energy curve yields re=3.74 Å, D0=328 cm−1, ωe=18.4 cm−1, and ωexe=0.28 cm−1 in reasonable agreement with experimental data (re=3.69±0.01 Å, De=380±25 cm−1, ωe=19.6±0.3 cm−1 and ωexe=0.25±0.05 cm−1). We finally present a scaled potential energy curve of the form ∑ja2jr−2j which fits the experimental fundamental vibrational transition of 19.1 cm−1 and the form of our calculated potential energy curve best (re=3.69 Å, D0=365 cm−1, ωe=19.7 cm−1, and ωexe=0.29 cm−1). We recommend these accurate two-body potentials as the starting point for the construction of many-body potentials in dynamic simulations of mercury clusters.

Analytic calculations are carried out for temperature and field dependences of the hopping drift mobility of charge carriers in strongly anisotropic disordered solids where transport can be treated as one dimensional. The solutions obtained are exact for hopping processes with noninteracting carriers and carrier transitions to the nearest sites in a one-dimensional chain. Only such transitions are essential in systems with strongly correlated space-energy distributions of localized states [see K. Kohary et al., following paper, Phys. Rev. B 63, 094202 (2001)]. Comparison is given for results obtained with symmetrical and asymmetrical transition rates. It is shown that mesoscopic effects play an essential role even for rather long chains with hundreds of localization sites. Moreover, not only the magnitude of the drift mobility, but also its temperature dependence is influenced by the chain length. A suggested theoretical description provides a general basis for the treatment of transport processes in one-dimensional disordered organic solids, such as columnar discotic liquid-crystalline glasses.

We present the first reliable determination of the line shape of the collision induced Raman spectrum of mercury vapour down to frequencies of about 1.5cm-1 at temperatures which are low enough that bound dimers make an important contribution to the spectrum. These new data are accurate enough to permit for the first time a reliable determination of the anisotropy of the mercury diatom as a function of the interatomic separation.

Interesting results were obtained in the initial investigation of the nucleation behavior of supersaturated sulfur vapor up to temperatures above the transition. This is a second-order phase transition in liquid sulfur characterized by a change in molecular structure from closed sulfur rings to open radical chains within a narrow temperature range. Although the temperature dependence of the constant rate supersaturation is not correctly represented, it is surprising again how well classical nucleation theory describes experimental results even for such a complex substance. For homogeneous nucleation, there are indications that the gimel transition influences the nucleation behavior as a consequence of the changing thermophysical properties - density and surface tension - of the liquid sulfur. Photoinduced nucleation shows a striking effect directly correlated with the transition. Below the gimel temperature, the vapor is extremely sensitive to irradiation with light in the range 260-360 nm that decreases the constant rate supersaturation by about a factor of 10. At the transition temperature, the photo effect vanishes sharply. The close correlation of the structure of liquid sulfur and the nucleation behavior is interpreted as a confirmation of the capillarity approximation that indeed the properties of the liquid determine nucleation behavior.

Anomalous X-ray scattering experiments have been performed for glassy (g-) As2Se3 at room temperature and for liquid (l–) As2Se3 at 400 °C in order to clarify the role of each constituent for the short- and intermediate-range order (SRO and IRO). The differential structure factors ΔiS(Q)s close to the As and Se K edges have been obtained from a detailed analysis. The first nearest neighbour distances around both As and Se are about 0.24±0.02nm for both g- and l-As2Se3, which would support the SRO model that g- and l-As2Se3 have an SRO similar to the corresponding crystal. The prepeak in S(Q) for g-As2Se3 seems to be dominated by a partial structure factor SAsAs(Q), which reveals the existence of the As–As IRO with a correlation length of about 0.52 nm. In l-As2Se3, however, the substitution of Se atoms into some As sites would cause a contribution in ΔseS(Q) at the prepeak position.

Drift mobility of charge carriers in strongly anisotropic disordered organic media is studied by Monte Carlo computer simulations. Results for the nearest-neighbor hopping are in excellent agreement with those of the analytic theory (Cordes et al., preceding paper). It is widely believed that the low-field drift mobility in disordered organic solids has the form mu infinity exp[-(T-0/T)(2)] with characteristic temperature T-0 depending solely on the scale of the energy distribution of localized states responsible for transport. Taking into account electron transitions to more distant sites than the nearest neighbors, we show that this dependence is not universal and parameter T-0 depends also on the concentration of localized states and on the decay length of the electron wave function in localized states. The results of computer simulation evidence that correlations in the distribution of localized states influence essentially not only the held dependence as known from the literature, but also the temperature dependence of the drift mobility. In particular, strong space-energy correlations diminish the role of long-range hopping transitions in the charge carrier transport.

Liquid Te just above the melting point is a poor metal. Its structure is assumed to consist of short chains of covalently bound atoms, with strong chain-chain interaction causing metallic like properties. To study the temperature dependence of this structural arrangement, energy dispersive X-ray diffraction measurements were carried out on liquid Te in a temperature range between 500 and 1700 degreesC and applied pressure of 50 bar. It is found that the position of the first peak in the structure factor is located around 2.1 Angstrom (-1) at 500 degreesC and shifts to 2.25 Angstrom (-1) for temperatures above 1300 degreesC. Additionally, an increase in the scattering intensity is observed around 1.4 Angstrom (-1) with rising temperature. The structural variations also influence the corresponding pair distribution functions, With increasing temperature. the first co-ordination shell shifts to larger distances but remains at a constant position above 1100 degreesC, suggesting a structural transition in this temperature range. This view is supported by temperature induced changes which are observed in the second coordination shell. (C) 2001 Elsevier Science B.V. All rights reserved.

An analytic theoretical description of transport processes based on the concept of transport energy is suggested for disordered organic solids. It gives not only the natural explanation of experimental data but also accounts for the results of computer simulations considered so far puzzling. In particular, this approach accounts for the strong difference between the temperature dependence of the carrier drift mobility and that of the relaxation time. Experimental data for the low-field drift mobility display the temperature dependence in the form $\ensuremath{\mu}\ensuremath{\propto}\mathrm{exp}{\ensuremath{-}{(T}_{0}{/T)}^{2}}.$ It is believed that the characteristic temperature ${T}_{0}$ is determined solely by the scale of the energy distribution of localized states, and such a temperature dependence of \ensuremath{\mu} is widely used to determine this energy scale from experimental data for various materials. We show that this temperature dependence is not universal and that parameter ${T}_{0}$ depends also on the concentration of localized states and on the decay length of the carrier wave function in the localized states. The suggested theory provides a general basis for the treatment of transport processes in disordered organic media.