Equation Of State Transition Research Articles

Quasi-monoenergetic heavy ion acceleration driven by sub-100 PW linearly polarized laser pulses in the radiation-dominated QED regime

Heavy ion acceleration from an ultrathin foil target irradiated by a p-polarized and spatially Gaussian laser pulse at intensity of 1023 W/cm2 is studied by using two-dimensional particle-in-cell simulations. We find that, in the extremely intense laser fields, the radiation reaction force from bright γ-rays radiated by radially oscillating electrons is large enough to match the Coulomb explosive force of foil electrons. The undesirable transverse expansion of the foil from the electron heating and inhomogeneous radial profile of the laser intensity is effectively suppressed. The foil maintains relatively good opacity in its central region stabilizing localized acceleration of heavy ions. With a laser of intensity 3.4 × 1023 W/cm2, duration of 33 fs, and power of 96 PW, a dense monoenergetic Au79+ ion bunch with a peak energy of ∼160 GeV can be obtained in the radiation-dominated QED regime. Such a high-quality heavy ion beam is useful for investigating nuclear matter equation of state and quantum chromodynamic phase transition in intermediate-energy heavy ion collisions.

Dense matter equation of state and phase transitions from a generalized Skyrme model

Skyrmion crystals are the field configurations which minimize the energy per baryon in the infinitely large topological charge sector of the Skyrme model, at least for sufficiently high density. They are, therefore, an important tool to describe the ground state of cold, symmetric nuclear matter at high density regimes. In this work, we analyze different crystalline phases and the existence of phase transitions between them within the generalized Skyrme model, with the ultimate goal of describing symmetric nuclear matter in a wide regime of densities. Furthermore, we propose a new energy-minimizing phase for densities lower than the nuclear saturation point (${n}_{0}$) that also presents a good qualitative behavior in the zero density limit, thereby improving the description of strongly interacting matter in the region $n<{n}_{0}$.

Phase transition and equation of state of dense liquid nitrogen at high temperature and high pressure

Nitrogen is the main reaction and detonation product of energetic materials. Therefore, studying the equation of state and phase transition of nitrogen at high temperature and high pressure is very important in evaluating the energy characteristics of energetic materials, especially in designing a new-generation nitrogen-rich energetic materials. Using density functional molecular dynamics simulation method, we calculate the pressure, internal energy and chemical components of fluid nitrogen in a temperature range of 900–25000 K and a pressure range of 2–300 GPa. The negative changes of pressure with temperature on isochores are observed under the temperature and pressure conditions of 3000–10000 K and 20–80 GPa. As the temperature increases, the pressure drop is caused by the collapse of nitrogen molecules. This phenomenon is related to the phase transition from molecular fluid nitrogen to polymerized fluid nitrogen. The triple bond in the molecule breaks and a polymer forms, which is connected by single and double bonds with neighboring atom. We also study the equation of state along Hugoniot curve under impact loading. The obtained Hugoniot curve is in good agreement with the experimental results. It is found that the softening of the experimental curve in a range of 30–60 GPa is related to the decomposition of nitrogen molecules and the formation of polymeric nitrogen.

Probing Dense Nuclear Matter in the Laboratory: Experiments at FAIR and NICA

The poorly known properties of high-density strongly-interacting matter govern the structure of neutron stars and the dynamics of neutron star mergers. New insight has been and will be gained by astronomical observations, such as the measurement of mass and radius of neutron stars, and the detection of gravitational waves emitted from neutron star mergers. Alternatively, information on the Nuclear Matter Equation-of-State (EOS) and on a possible phase transition from hadronic to quark matter at high baryon densities can be obtained from laboratory experiments investigating heavy-ion collisions. Detector systems dedicated to such experiments are under construction at the “Facility for Antiproton and Ion Research” (FAIR) in Darmstadt, Germany, and at the “Nuclotron-based Ion Collider fAcility” (NICA) in Dubna, Russia. In heavy-ion collisions at these accelerator centers, one expects the creation of baryon densities of up to 10 times saturation density, where quark degrees-of-freedom should emerge. This article reviews the most promising observables in heavy-ion collisions, which are used to probe the high-density EOS and possible phase transition from hadronic to quark matter. Finally, the facilities and the experimental setups will be briefly described.

Equation of state and chiral transition in soft-wall AdS/QCD with a more realistic gravitational background * * Supported in part by the National Natural Science Foundation of China (NSFC) (11851302, 11851303, 11690022, 11747601), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB23030100) as well as the CAS Center for Excellence in Particle Physics (CCEPP). Z. F. is

We construct an improved soft-wall AdS/QCD model with a cubic coupling term of the dilaton and the bulk scalar field. The background fields in this model are solved by the Einstein-dilaton system with a nontrivial dilaton potential, which has been shown to reproduce the equation of state from the lattice QCD with two flavors. The chiral transition behaviors are investigated in the improved soft-wall AdS/QCD model with the solved gravitational background, and the crossover transition can be realized. Our study provides the possibility to address the deconfining and chiral phase transitions simultaneously in the bottom-up holographic framework.

First‐Principles Study of Thermodynamics and Spin Transition in FeSiO3 Liquid at High Pressure

AbstractThe thermodynamic properties of iron silicate liquids at high pressures and temperatures are poorly constrained, even though they are important for understanding the thermal and chemical evolution of a magma ocean. Here we report the results of the P‐V‐T equation of state, thermodynamic properties, and spin transition of iron in FeSiO3 liquid at 2500–6000 K and pressure conditions spanning the entire mantle using first‐principles molecular dynamics simulations. Our calculations predict that FeSiO3 liquid undergoes a linear high‐to‐low spin transition over a broad pressure interval (>296 GPa), and the spin state of iron in FeSiO3 liquid is mainly the high‐spin state near the conditions of the core‐mantle boundary. Our results of FeSiO3 liquid adiabats show that iron content has little effect on the adiabatic temperature profile of liquid (Mg,Fe)SiO3 in a magma ocean.

Boron monosulfide: Equation of state and pressure-induced phase transition

Quasi-hydrostatic compression of rhombohedral boron monosulfide (r-BS) has been studied up to 50 GPa at room temperature using diamond-anvil cells and angle-dispersive synchrotron X-ray diffraction. A fit of the experimental P–V data to the Vinet equation of state yields the bulk modulus B0 of 42.2(1.4) GPa and its first pressure derivative B0′ of 7.6(2) that are in excellent agreement with our ab initio calculations. Formation of a new high-pressure phase of boron monosulfide (hp-BS) has been observed above 35 GPa. According to ab initio evolutionary crystal structure predictions combined with Rietveld refinement of high-pressure X-ray diffraction data, the structure of hp-BS has trigonal symmetry and belongs to the space group P-3m1. As it follows from the electron density of state calculations, the phase transformation is accompanied by an insulator-metal transition.

Isothermal equation of state and high-pressure phase transitions of synthetic meridianiite (MgSO4·11D2O) determined by neutron powder diffraction and quasielastic neutron spectroscopy

We have collected neutron powder diffraction data from MgSO4·11D2O (the deuterated analogue of meridianiite), a highly hydrated sulfate salt that is thought to be a candidate rock-forming mineral in some icy satellites of the outer solar system. Our measurements, made using the PEARL/HiPr and OSIRIS instruments at the ISIS neutron spallation source, covered the range 0.1 < P < 800 MPa and 150 < T < 280 K. The refined unit-cell volumes as a function of P and T are parameterized in the form of a Murnaghan integrated linear equation of state having a zero-pressure volume V 0 = 706.23 (8) Å3, zero-pressure bulk modulus K 0 = 19.9 (4) GPa and its first pressure derivative, K′ = 9 (1). The structure's compressibility is highly anisotropic, as expected, with the three principal directions of the unit-strain tensor having compressibilities of 9.6 × 10−3, 3.4 × 10−2 and 3.4 × 10−3 GPa−1, the most compressible direction being perpendicular to the long axis of a discrete hexadecameric water cluster, (D2O)16. At high pressure we observed two different phase transitions. First, warming of MgSO4·11D2O at 545 MPa resulted in a change in the diffraction pattern at 275 K consistent with partial (peritectic) melting; quasielastic neutron spectra collected simultaneously evince the onset of the reorientational motion of D2O molecules with characteristic time-scales of 20–30 ps, longer than those found in bulk liquid water at the same temperature and commensurate with the lifetime of solvent-separated ion pairs in aqueous MgSO4. Second, at ∼ 0.9 GPa, 240 K, MgSO4·11D2O decomposed into high-pressure water ice phase VI and MgSO4·9D2O, a recently discovered phase that has hitherto only been formed at ambient pressure by quenching small droplets of MgSO4(aq) in liquid nitrogen. The fate of the high-pressure enneahydrate on further compression and warming is not clear from the neutron diffraction data, but its occurrence indicates that it may also be a rock-forming mineral in the deep mantles of large icy satellites.

Primordial equation of state transitions

We revisit the physics of transitions from a general equation of state parameter to the final stage of slow-roll inflation. We show that it is unlikely for the modes comprising the cosmic microwave background to contain imprints from a pre-inflationary equation of state transition and still be consistent with observations. We accomplish this by considering observational consistency bounds on the amplitude of excitations resulting from such a transition. As a result, the physics which initially led to inflation likely cannot be probed with observations of the cosmic microwave background. Furthermore, we show that it is unlikely that equation of state transitions may explain the observed low multipole power suppression anomaly.

High pressure phase transition of Ce–La alloy from first-principles calculations

We report the γ–α isostructural transition and α-bct phase transition in Ce–La alloy under pressure within the generalized gradient approximation plus on-site Coulomb interaction (GGA+U) method. The equation of state and volume collapse transition between γ and α phases were predicted. By using quasi-harmonic Debye model, we obtained the γ–α transition boundary. The predicted γ–α transition pressures increase with the increasing temperature and the increasing La concentration in the Ce–La alloy.

Equation of state and structural phase transitions in iron-based Ba3TaFe3Si2O14 langasite at high hydrostatic pressures

Synchrotron X-ray diffraction studies of the structural characteristics of Ba3TaFe3Si2O14 langasite are performed at high hydrostatic pressures (up to 60 GPa) created in a diamond anvil cell. At pressures up to 20 GPa, the Mossbauer absorption spectra for 57Fe nuclei and the Raman spectra are recorded. Two structural phase transitions at P ≈ 5.5 and 20 GPa are observed. The first transition corresponds to the displacements of light oxygen atoms and to an increase in the local symmetry of 3f oxygen tetrahedra surrounding iron ions. The second one is accompanied by a pronounced change in the lattice parameter c, and the unit cell volume undergoes a stepwise drop as large as 8.6%. An appreciable decrease in the parameter c at the structural transition should result in a significant increase in the exchange coupling constants between iron ions in neighboring ab planes underlying the giant increase in the Neel temperature in this crystal at pressures exceeding 20 GPa.

Benchmarking Surface Position from Laser Velocimetry with High-Speed Video in Impact Experiments

Photonic Doppler Velocimetry (PDV) is a heterodyne laser interferometric technique for computing the velocities of free surfaces moving up to tens of kilometers per second. This information can be used to infer material properties such as equation of state and phase transitions, many of which are unknown even for common materials like steel. Broadly speaking, the methods of computing velocity from the voltages measured on an oscilloscope are either local or global in time, either frequency-based or phase-based, and formulated either statistically or deterministically. It is important to understand how velocities extracted using the different classes of methods relate to each other and how the results relate to measurements from independent diagnostics. In this work we present computed surface velocities of a flat plate of stainless steel impacted by a projectile traveling approximately 4km/s from a light gas gun, using several different extraction methods, and we benchmark the results of the different PDV analyses against high-speed video captured at 5 million frames per second with a hybrid framing-video camera. The different extraction methods all show the same large-scale structures in the computed velocity profiles–and they agree with the high-speed video at the appropriate time scale–but they each show different small-scale features. We discuss the nature of these features, including descriptions of the numerical artifacts that one would expect with each of the different analysis techniques applied. Descriptions of the methods are provided, with a focus on the Local Polynomial Approximation method, and its uncertainty quantification, developed by the authors.

Equation of state and phase transition in spin-orbit-coupled Bose gases at finite temperature: A perturbation approach

We study two-component Bose gases with Raman induced spin-orbit coupling via a perturbation approach at finite temperature. For weak coupling, free energy is expanded in terms of Raman coupling strength up to the second order, where the coefficient (referred to as Raman susceptibility) is determined according to linear response theory. The equation of state for the stripe phase and the plane-wave phase are obtained in Popov approximation, and the first order transition between these two phases is investigated. As temperature increases, we find the phase boundary bends toward the stripe phase side in most temperature regions, which implies the ferromagnetic order is more robust than the crystalline order in presence of thermal fluctuations. Our results qualitatively agree with the recent experimental observation in rubidium atomic gases. A method to measure the Raman susceptibility through the two-photon Bragg scattering experiment is also discussed.

Phase transitions and equation of state of forsterite to 90 GPa from single-crystal X-ray diffraction and molecular modeling

Forsterite, Mg2SiO4, the magnesian end-member of the olivine system, is the archetypal example of an orthosilicate structure. We have conducted synchrotron-based single-crystal X-ray diffraction experiments to 90 GPa on synthetic end-member forsterite to study its equation of state and phase transitions. Upon room-temperature compression, the forsterite structure is observed to 48 GPa. By fitting a third-order Birch-Murnaghan equation of state to our compression data, we obtain the zero-pressure isothermal bulk modulus, K 0T = 130.0(9) GPa and its pressure derivative, K ′0T = 4.12(7) for a fixed room-pressure volume, V = 290.1(1) A3, in good agreement with earlier work. At 50 GPa, a phase transition to a new structure (forsterite II) occurs, followed by a second transition to forsterite III at 58 GPa. Forsterite III undergoes no additional phase transitions until at least 90 GPa. There is an ~4.8% volume reduction between forsterite and forsterite II, and a further ~4.2% volume reduction between forsterite II and III. On decompression forsterite III remains until as low as 12 GPa, but becomes amorphous at ambient conditions. Using our X-ray diffraction data together with an evolutionary crystal structure prediction algorithm and metadynamics simulations, we find that forsterite II has triclinic space group P 1 and forsterite III has orthorhombic space group Cmc 21. Both high-pressure phases are metastable. Metadynamics simulations show a stepwise phase transition sequence from 4-coordinated Si in forsterite to mixed tetrahedral and octahedral Si (as in forsterite II), and then fully sixfold-coordinated Si (as in forsterite III), occurring by displacement in \[001\](100). The forsterite III structure is a member of the family of post-spinel structures adopted by compositions such as CaFe2O4 and CaTi2O4.

Thermal equation of state and spin transition of magnesiosiderite at high pressure and temperature

In situ synchrotron X-ray diffraction experiments on natural magnesiosiderite [(Mg0.35Fe0.65)CO3] were conducted using resistive and laser-heated diamond-anvil cells (DACs) up to 78 GPa and 1200 K. Based on thermal elastic modeling of the measured pressure-volume curves at given temperatures, we have derived thermal equation of state (EoS) parameters and the spin-crossover diagram of magnesiosiderite across the spin transition. These results show the spin crossover broadened and shifted toward higher pressures at elevated temperatures. Low-spin magnesiosiderite is 6% denser and 8% more incompressible than the high-spin phase at 1200 K and high pressures. Within the spin crossover from 53 to 63 GPa at 1200 K, magnesiosiderite exhibits anomalous thermal elastic behaviors, including a dramatic increase in the thermal expansion coefficient by a factor of 20 and a drop in the isothermal bulk modulus and the bulk sound velocity by approximately 75 and 50%, respectively. Compared with the end-member magnesite [MgCO3] at relevant pressure-temperature conditions of the subducted slabs, the high-spin magnesiosiderite with 65 mol% FeCO3 is approximately 21-23% denser and its unit-cell volume is 2-4% larger, whereas the low-spin state is 28-29% denser and 2% smaller than the end-member magnesite. Since ferromagnesite with 20 mol% of iron has been proposed to be a potential deep-carbon carrier, our results here indicate that the dense low-spin ferromagnesite can become more stable than high-spin ferromagnesite at pressures above approximately 50 GPa, providing a mechanism for (MgFe)-bearing carbonate to be a major carbon host in the deeper lower mantle.

REVIEW OF RECENT RESULTS FROM THE RHIC BEAM ENERGY SCAN

We review recent results from the RHIC beam energy scan (BES) program, aimed to study the Quantum Chromodynamics (QCD) phase diagram. The main goals are to search for the possible phase boundary, softening of equation of state or first order phase transition, and possible critical point. Phase-I of the BES program has recently concluded with data collection for Au+Au collisions at center-of-mass energies [Formula: see text] of 7.7, 11.5, 19.6, 27 and 39 GeV. Several interesting results are observed for these lower energies where the net-baryon density is high at the mid-rapidity. These results indicate that the matter formed at lower energies (7.7 and 11.5 GeV) is hadron dominated and might not have undergone a phase transition. In addition, a centrality dependence of freeze-out parameters is observed for the first time at lower energies, slope of directed flow for (net)-protons measured versus rapidity shows an interesting behavior at lower energies, and higher moments of net-proton show deviation from Skellam expectations at lower energies. An outlook for the future BES Phase-II program is presented and efforts for the detailed study of QCD phase diagram are discussed.

Equation of state and phase transition of antigorite under high pressure and high temperature

The equation of state of natural antigorite has been determined up to ∼10GPa and 500°C by in situ X-ray diffraction in a cubic type multi-anvil apparatus, MAX80, located at the Photon Factory-Advanced Ring at the High Energy Accelerator Research Organization (KEK), and the temperature dependence of the bulk modulus was determined for the first time by high pressure and high temperature X-ray diffraction based on a series of direct measurements. No dehydration occurred during the entire experimental process, and no significant deviatoric stress was observed after heating. The room temperature P–V data below 7GPa have been fit to the Birch-Murnaghan equation of state, yielding V0,300K=366.9(7)Å3, K0, 300K=65.2(31)GPa, and the pressure derivative K′ fixed to 6.1. The high pressure phase transition was observed through volume softening behavior at around 7GPa, and the dP/dT slope seems to be flat or slightly positive, which is consistent with the recent report by Bezacier et al. (2013). The high temperature Birch-Murnaghan equation of state was used to fit the P–V–T data below 7GPa. Since the present experimental data was obtained by energy dispersive X-ray diffraction at high pressure and high temperature, the resolution was slightly lower than that obtained by the angle dispersive X-ray method. So the bulk modulus K0, 300K and the pressure derivative K′ were fixed to 62.9GPa and 6.1, respectively, which was obtained by single crystal X-ray diffraction in a diamond anvil cell by means of the angle dispersive method (Nestola et al., 2010) during fitting. From the fitting, we obtained V0, 300K=367.3(2)Å3, dK/dT=−0.0265(41)GPa/K, thermal expansion α0=3.92(50)×10−5/K. The temperature dependence of the bulk modulus was larger than the value calculated empirically (Holland and Powell, 1998). The thermal expansion of antigorite is larger than the results from the previous study. The compression of antigorite is very anisotropic along three axes, with a ratio of 1.15:1.00:3.33 at room temperature. Considering the P–T conditions of the subducting slab, the phase transition of antigorite may occur only in a limited area in the slab.

Modeling of Earthwork Dynamic Allocation for Rock-Fill Dams

By analyzing feeding sources and material accepted fields involved in the earthwork allocation for rock-fill dam, a dynamic model of earthwork allocation is set up by incorporating dynamic programming. Dividing filling and excavation process into n steps, functions of allocation costs during each period is defined according to equation of state transitions, on the basis of which the optimization function is formed. Then the sequential method is employed to get the optimized solution. Finally a practical case is studied for application of this model.

Structural and chemical properties of the nitrogen-rich energetic material triaminoguanidinium 1-methyl-5-nitriminotetrazolate under pressure

The structural and chemical properties of the bi-molecular, hydrogen-bonded, nitrogen-rich energetic material triaminoguanidinium 1-methyl-5-nitriminotetrazolate C(3)H(12)N(12)O(2) (TAG-MNT) have been investigated at room pressure and under high pressure isothermal compression using powder x-ray diffraction and Raman and infrared spectroscopy. A stiffening of the equation of state and concomitant structural relaxation between 6 and 14 GPa are found to correlate with Raman mode disappearances, frequency discontinuities, and changes in the pressure dependence of modes. These observations manifest the occurrence of a reversible martensitic structural transformation to a new crystalline phase. The onset and vanishing of Fermi resonance in the nitrimine group correlate with the stiffening of the equation of state and phase transition, suggesting a possible connection between these phenomena. Beyond 15 GPa, pressure induces irreversible chemical reactions, culminating in the formation of a polymeric phase by 60 GPa.

A pressure-induced amorphous phase transition in magnesium-substituted [formula omitted]-tricalcium phosphate

Synchrotron-based X-ray diffraction was used to determine the equation of state and phase transition in magnesium-substituted β -tricalcium phosphate ( β -TCMP). It was observed that β -TCMP undergoes a phase transformation from a rhombohedral unit cell to an amorphous structure. This pressure-induced amorphization is reversible from ∼32 GPa under quasi-hydrostatic conditions and irreversible when quenched from ∼57 GPa in non-hydrostatic conditions. Based upon the quasi-hydrostatic equation of state, the bulk modulus for the crystalline phase of the material was calculated to be 80.6±3.1 GPa.