摘要:

In 1956 P. W. Bridgman published a letter to the editor in the Journal of Applied Physics reporting results of electrical resistance measurements on iron under static high pressure. The work was undertaken to verify the existence of a polymorphic phase transition at 130 kbar (13 GPa) reported in the same journal and year by the Los Alamos authors, Bancroft, Peterson, and Minshall for high pressure, shock‐compression loading. In his letter, Bridgman reported that he failed to find any evidence for the transition. Further, he raised some fundamental concerns as to the state of knowledge of shock‐compression processes in solids. Later it was determined that Bridgman’s static pressure scale was in error, and the shock observations became the basis for calibration of pressure values in static high pressure apparatuses. In spite of the error in pressure scales, Bridgman’s concerns on descriptions of shock‐compression processes were perceptive and have provided the basis for subsequent fundamental studies of shock‐compressed solids. The present paper, written in response to receipt of the 1993 American Physical Society Shock‐Compression Science Award, provides a brief contemporary assessment of those shock‐compression issues which were the basis of Bridgman’s 1956 concerns. © 1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46127

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

It is a great pleasure and honor to receive the Percy Williams Bridgman Award. Henry Eyring, my Ph.D. advisor, instilled in me a desire to unravel the secrets of nature in the chemical and physical world. He continued what my mother had begun. From my father I learned the virtue and satisfaction of hard work. In reading Percy Bridgman’sThe Physics of High Pressure[1] after I came to Cornell, I became intrigued by the high‐pressure variable, so I owe much to him. I received valuable assistance and encouragement from George Kennedy and Harry Drickamer (the first winner of the Bridgman Award) and later from Alvin Van Valkenburg (a co‐inventor with three others of the diamond anvil cell). Most importantly, I received encouragement from my wife, Enid Seaton Ruoff, to carry out what is sometimes the arduous pursuit of science—a pursuit that involves long working hours—and I want especially to thank her. © 1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46241

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Impulsive Stimulated Scattering in the form of Laser‐Induced Phonon Spectroscopy is applied to the measurement of elastic moduli in the diamond‐anvil high‐pressure cell. In general ISS offers an approach to the study of a variety of equilibrium and dynamic phenomena in small solid and liquid samples. The requirements of the diamond‐anvil cell do not impose a severe obstacle to the repetition, at high pressure and temperature, of many experiments which have proven successful at ambient conditions. In particular, the pressure dependence of elastic constants and thermal diffusivity of &bgr;–oxygen are shown. Measurements of the viscoelastic properties of methanol at high temperature and pressure have also been completed. © 1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46116

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

&agr;‐Quartz undergoes metastable phase transformations when statically compressed outside of its stability field at 300 K. Crystalline‐crystalline and crystalline‐amorphous transformations in &agr;‐quartz are documented by a variety of techniques which probe the structure from macroscopic to interatomic length scales. Material recovered from static &agr;‐quartz compression experiments exhibits a number of similarities to quartz experiencing shock compression and comminution. © 1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46126

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Two pressure‐induced phase transitions have been observed in sulfur in a pressure range of 0–32 GPa by the EDXD techniques using a synchrotron source. These two phase transitions are: (1) the original &agr;‐S8to a monoclinic phase at about 5 GPa; (2) the monoclinic phase to an amorphous phase completed at about 25 GPa. The crystalline‐amorphous transition was found to be reversible with hysteresis upon decreasing pressure. A mechanism of this pressure‐induced amorphization of sulfur is proposed. In a very recent experiment on sulfur, we have extended pressure range to 212 GPa and observed additional phase transitions to a base‐centered orthorhombic phase at about 90 GPa (which had been observed previously) and then to the &bgr;‐Po phase at 162±5 GPa. The equation of state of sulfur was determined to 212 GPa. © 1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46137

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Thermal internal energy in the Gru¨neisen equation of state is found to be decomposed into two new thermal variables, &THgr;(v) and C(S), like temperature T and entropy S. The variable &THgr; is found to correspond to the Debye temperature. Relationship between the variable C and the specific heat Cv might be universal, as long as the Debye model for the specific heat is valid. © 1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46084

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

In the sixties, the first author and by P. Savic´ and R. Kasˇanin started developing a mean‐field theory of dense matter. It is based on the Coulomb interaction, supplemented by a microscopic selection rule and a set of experimentally founded postulates. Applications of the theory range from the calculation of models of planetary internal structure to DAC experiments. © 1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46093

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

There has been recently, in the field of high pressure physics in particular, a large number of publications on various ‘‘universal’’ equations of state, or ‘‘nearly universal’’ expressions. In the present paper we shall show that the resulting proliferation of different scaling factors and reduced expressions may be redundant since most of them can be shown to be equivalent. The mathematical processes developed by the different authors lead in general to some degree of arbitrariness in the choice of scaling factors, preventing the obtention of a consistent set of reduced variables. We shall also show that such a set can be obtained in a straightforward way from similarity considerations. © 1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46103

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Recent experiments to measure electrical conductivities and temperatures of liquid hydrogen shock‐compressed up to Mbar pressures are described and contrasted with results for liquid nitrogen. Some thoughts about future possibilities for high‐pressure shock experiments are discussed. © 1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46409

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The NatomsPT Monte Carlo simulation method has been reformulated to incorporate multiple species and chemical reactions with changes in the total number of molecules. While maintaining a constant number of each type of atom, the number of molecules is changed by turning on and off the interactions of any particular molecular position with other molecules. Chemical reactions are allowed as a correlated move of atoms to different molecular locations. Equilibrium chemical composition is determined as an average over the simulation along with equation of state quantities. A large set of simulations has been made with the systemN2+O2&rlarr2;NOcovering a wide range in P and T. Both Hugoniot states and the CJ point have been determined and are shown to be sensitive to the potentials between unlike species. © 1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46419

出版商:AIP    

年代:1994

数据来源: AIP