Laser-heated Experiments Research Articles

Phase transition kinetics of superionic H2O ice phases revealed by Megahertz X-ray free-electron laser-heating experiments

H2O transforms to two forms of superionic (SI) ice at high pressures and temperatures, which contain highly mobile protons within a solid oxygen sublattice. Yet the stability field of both phases remains debated. Here, we present the results of an ultrafast X-ray heating study utilizing MHz pulse trains produced by the European X-ray Free Electron Laser to create high temperature states of H2O, which were probed using X-ray diffraction during dynamic cooling. We confirm an isostructural transition during heating in the 26-69 GPa range, consistent with the formation of SI-bcc. In contrast to prior work, SI-fcc was observed exclusively above ~50 GPa, despite evidence of melting at lower pressures. The absence of SI-fcc in lower pressure runs is attributed to short heating timescales and the pressure-temperature path induced by the pump-probe heating scheme in which H2O was heated above its melting temperature before the observation of quenched crystalline states, based on the earlier theoretical prediction that SI-bcc nucleates more readily from the fluid than SI-fcc. Our results may have implications for the stability of SI phases in ice-rich planets, for example during dynamic freezing, where the preferential crystallization of SI-bcc may result in distinct physical properties across mantle ice layers.

The Thermal Conductivity of Bridgmanite at Lower Mantle Conditions Using a Multi‐Technique Approach

AbstractThe thermal conductivity of bridgmanite, the primary constituent of the Earth's lower mantle, has been investigated using diamond anvil cells at pressures up to 85 GPa and temperatures up to 3,100 K. We report the results of time‐domain optical laser flash heating and X‐ray Free Electron Laser heating experiments from a variety of bridgmanite samples with different Al and Fe contents. The results demonstrate that Fe or Fe,Al incorporation in bridgmanite reduces thermal conductivity by about 50% in comparison to end‐member MgSiO3 at the pressure‐temperature conditions of Earth's lower mantle. The effect of temperature on the thermal conductivity at 28–60 GPa is moderate, well described as , where a is 0.2–0.5. The results yield thermal conductivity of 7.5–15 W/(m × K) in the thermal boundary layer of the lowermost mantle composed of Fe,Al‐bearing bridgmanite.

High-pressure Phase Transition of Olivine-type Mg2GeO4 to a Metastable Forsterite-III type Structure and their Equation of States

Abstract Germanates are often used as structural analogs of planetary silicates. We have explored the high-pressure phase relations in Mg2GeO4 using diamond anvil cell experiments combined with synchrotron X-ray diffraction and computations based on density functional theory. Upon room temperature compression, forsterite-type Mg2GeO4 remains stable up to 30 GPa. At higher pressures, a phase transition to a forsterite-III type (Cmc21) structure was observed, which remained stable to the peak pressure of 105 GPa. Using a 3rd order Birch Murnaghan fit to the experimental data, we obtained V0 = 305.1 (3) Å3, K0 = 124.6 (14) GPa and K0′ = 3.86 (fixed) for forsterite- and V0 = 263.5 (15) Å3, K0 = 175 (7) GPa and K0′ = 4.2 (fixed) for the forsterite-III type phase. The forsterite-III type structure was found to be metastable when compared to the stable assemblage of perovskite/post-perovskite + MgO, as observed during laser-heating experiments. Understanding the phase relations and physical properties of metastable phases is crucial for studying the mineralogy of impact sites, understanding metastable wedges in subducting slabs and interpreting the results of shock compression experiments.

Thermal equation of state of rhodium to 191 GPa and 2700 K using double-sided flash laser heating in a diamond anvil cell

The phase behavior of rhodium (Rh) metal has been studied to 191 GPa and 2700 K using a combination of room-temperature isothermal compression and double-sided flash laser heating experiments. The isothermal compression data have been fitted with a second-order adapted polynomial of order L equation of state (EoS) with best-fitting parameters of V0=13.764(2)Å3/atom, K0=258(3)GPa, and K′=5.36(9). Two-dimensional maps of the uniaxial stress component t are presented for Rh at different pressures showing the spatial distribution of the local stress state of a relatively high-yield strength material encased in a Bi pressure medium. In addition, a simple, thermal pressure equation-of-state model, based on a single Einstein temperature, has been fitted to the high-pressure-temperature data up to 2700 K at 148 GPa and ambient-pressure thermal expansion data up to 1982 K. Also determined are the best-fitting parameters to reproduce the thermal EoS within the two-dimensional integration software. The optimized parameters are V0=13.764Å3/atom, K0=260.54GPa, K′=5.114, αT=2.99×10−5 K−1, ∂αT/∂T=1.27×10−9 K−2, ∂K0/∂T=−6.43×10−5GPa/K, and ∂K′/∂T=−9.3×10−10K−1. Published by the American Physical Society 2024

Overcoming aggregation with laser heated nanoelectrospray mass spectrometry: thermal stability and pathways for loss of bicarbonate from carbonic anhydrase II.

Variable temperature electrospray mass spectrometry is useful for multiplexed measurements of the thermal stabilities of biomolecules, but the ionization process can be disrupted by aggregation-prone proteins/complexes that have irreversible unfolding transitions. Resistively heating solutions containing a mixture of bovine carbonic anhydrase II (BCAII), a CO2 fixing enzyme involved in many biochemical pathways, and cytochrome c leads to complete loss of carbonic anhydrase signal and a significant reduction in cytochrome c signal above ∼72 °C due to aggregation. In contrast, when the tips of borosilicate glass nanoelectrospray emitters are heated with a laser, complete thermal denaturation curves for both proteins are obtained in <1 minute. The simultaneous measurements of the melting temperature of BCAII and BCAII bound to bicarbonate reveal that the bicarbonate stabilizes the folded form of this protein by ∼6.4 °C. Moreover, the temperature dependences of different bicarbonate loss pathways are obtained. Although protein analytes are directly heated by the laser for only 140 ms, heat conduction further up the emitter leads to a total analyte heating time of ∼41 s. Pulsed laser heating experiments could reduce this time to ∼0.5 s for protein aggregation that occurs on a faster time scale. Laser heating provides a powerful method for studying the detailed mechanisms of cofactor/ligand loss with increasing temperature and promises a new tool for studying the effect of ligands, drugs, growth conditions, buffer additives, or other treatments on the stabilities of aggregation-prone biomolecules.

A laser-based system to heat nuclear fuel pellets at high temperature.

Annealing tests are of utmost importance in nuclear fuel research, particularly to study the thermophysical properties of the material, microstructure evolution, or the released gas as a function of temperature. As an alternative to conventional furnace or induction annealing, we report on a laser-heating experiment allowing one to heat a nuclear fuel pellet made of uranium dioxide, UO2, or potentially other nuclear fuel pellets in an isothermal and controlled manner. For that purpose, we propose to use an indirect heating method based on a two compartment tungsten crucible, one containing the sample and the other acting as a laser susceptor for efficient and homogeneous heating of the assembly. With this concept, we demonstrate the heating of UO2 samples up to 1500 °C at a maximum heating rate of 30 °C/s with the use of two 500W lasers. The system is, however, scalable to higher heating rates or higher temperatures by increasing the laser power up to few kW. The experiment has been designed to heat a pressurized water reactor fuel pellet, but the concept could be easily applied to other sample geometries or materials.

Seven-Coordinated High-Pressure Phase of CrSb2 and Experimental Equation of State of MSb2 (M = Cr, Fe, Ru, Os).

The MSb2 compounds with M = Cr, Fe, Ru, and Os have been investigated under high pressures by synchrotron powder X-ray diffraction. All compounds, except CrSb2, were found to retain the marcasite structure up to the highest pressures (more than 50 GPa). In contrast, we found that CrSb2 has a structural phase transition around 10 GPa to a metastable, MoP2-type structure with Cr coordinated to seven Sb atoms. In addition, we compared ambient temperature compression with laser-heating experiments and found that laser-heating at pressures below and above this phase transition results in the known CuAl2-type structure. Density functional theory calculations show that this tetragonal structure is the most stable in the whole pressure interval. However, a crossing of the marcasite's and MoP2-like structure's enthalpies occurs between 5 and 7.5 GPa, which is in good agreement with the experimental data. The phase transition to the MoP2-type structure observed in this work opens up for discovering other compounds with this new transition pathway from the marcasite structure.

Fully Coupled Material Response and Internal Radiative Heat Transfer for Three-Dimensional Heat Shield Modeling

A material response code is strongly coupled with a radiative transfer equation (RTE) to evaluate the effect of a spectrally resolved heat flux on the thermal response of a heat shield. A P1 approximation model of RTE is used to account for radiation heat transfer within the material. First, the RTE model is verified by comparing the numerical results with the analytical solution. Next, the coupling scheme is verified by comparing the temperature histories computed by the pure conduction scheme with the ones computed by conduction coupled with radiative emission. The verification study is conducted using test cases from the literature (radiant heating, arc jet heating, and space shuttle entry) as well as on a 3D Block, a 2D IsoQ sample, and the Stardust Return Capsule. The verification results are satisfactory for all cases. Thus, the verification results indicate that the coupling approach can accurately simulate the thermal response of the material. The coupling scheme was then used to simulate a laser heating experiment that studied the impact of spectral radiative heat transfer on ablative material. The results from the laser ablation simulations exhibit a behavior analogous to the experimental observations, indicating the importance of spectral radiative flux on the material response.

Physics-Informed Deep Learning for Solving Coupled Electron and Phonon Boltzmann Transport Equations

Electron-phonon (e-ph) coupling and transport are ubiquitous in modern electronic devices. The coupled electron and phonon Boltzmann transport equations (BTEs) hold great potential for the simulation of thermal transport in metal and semiconductor systems. However, solving the BTEs is often computationally challenging owing to their high dimensional complexity and a wide span of heat carrier properties, which hinder large-scale thermal modeling at the device level. In this work, we present a physics-informed neural network framework for solving the coupled electron and phonon BTEs. Instead of relying on labeled data, the proposed framework directly learns the spatiotemporal solutions (i.e., the electron and phonon distribution functions) within a parameterized space by enforcing physical laws. The efficacy of this framework is demonstrated through its ability to accurately resolve temperature profiles in low-dimensional thermal transport problems and visualize the ultrafast electron and phonon dynamics in laser heating experiments on thin metal films. The results indicate that our approach can accurately describe nonequilibrium e-ph energy transfer with improved efficiency, opening alternative avenues for the predictive design and optimization of micro- and nanostructures.

High-Pressure, High-Temperature Studies of Phase Transitions in SrOsO3─Discovery of a Post-Perovskite.

Using a recently developed method for in situ high-pressure, laser heating experiments in diamond anvil cells, we obtained a novel post-perovskite phase of SrOsO3. The phase transition from perovskite SrOsO3 was induced at 44 GPa and 1350 K in a diamond anvil cell and characterized with synchrotron powder X-ray diffraction. The newly obtained post-perovskite is quenchable and Le Bail refinements under ambient conditions yielded the unit cell parameters: a = 3.152(9) Å, b = 10.82(2) Å, c = 7.27(1) Å, V = 248.1(1) Å3. In addition, the compression of perovskite SrOsO3 at ambient temperature was investigated up to 66 GPa in a diamond anvil cell using synchrotron powder X-ray diffraction. The compression at ambient temperature showed that pressure alone does not induce the first-order phase transition to the post-perovskite structure. However, at 36 GPa, a continuous phase transition to monoclinic (P21/n) symmetry was detected, persistent up to 58 GPa, where the perovskite transitioned back to orthorhombic (Pbnm) symmetry. Fitting a third-order Birch-Murnaghan equation of state to the obtained P-V data for perovskite SrOsO3 yielded a bulk modulus of K0 = 187.4(15) GPa. Density functional theory calculations were performed to support the experimental findings in the compression study at ambient temperature. This work shows that transformations to the post-perovskite structure can be obtained for a wider range of perovskites than simple empirical rules otherwise suggest.

Experimental investigation on the ductile machinability of fused silica during in-situ laser assisted diamond cutting

Fused silica finds widespread applications in optical equipment; nevertheless, the machining of fused silica to obtain high-quality surfaces was a common problem in the industry. In-situ laser assisted diamond cutting (LADC) is a promising process for machining hard and brittle materials. In this study, systematic numerical analysis and experiments were conducted to investigate the ductile machinability of fused silica in in-situ LADC. The laser beam path and power density passing through the diamond tool were determined through optical simulation. The corresponding laser heating experiment of fused silica was carried out using the finite element (FE) simulation, aiming to derive the temperature distribution under different laser power levels. The comparison between the temperature values obtained experimentally and those predicted by the FE simulation confirmed the high accuracy of the developed FE model. The influence of laser power on the ductile machinability of fused silica was investigated quantitatively through grooving and end face turning experiments. The experimental results have shown that the ductility and machinability of fused silica under in-situ LADC were improved. With the laser assistance, the critical depth of cut (DOC) was increased up to 294.9 %, from 82.06 nm to 324.03 nm. Compared to conventional single point diamond turning, a significant improvement in the surface quality was obtained, resulting in the formation of a smooth and homogenous surface with a Sa of 19.4 nm for a laser power of 11 W.

Temperature acclimation in hot-spring snakes and the convergence of cold response

Animals have evolved sophisticated temperature-sensing systems and mechanisms to detect and respond to ambient temperature changes. As a relict species endemic to the Qinghai-Tibet Plateau, hot-spring snake (Thermophis baileyi) survived the dramatic changes in climate that occurred during plateau uplift and ice ages, providing an excellent opportunity to explore the evolution of temperature sensation in ectotherms. Based on distributional information and behavioral experiments, we found that T. baileyi prefer hot-spring habitats and respond more quickly to warmth than other two snakes, suggesting that T. baileyi may evolve an efficient thermal-sensing system. Using high-quality chromosome-level assembly and comparative genomic analysis, we identified cold acclimation genes experiencing convergent acceleration in high-altitude lineages. We also discovered significant evolutionary changes in thermosensation- and thermoregulation-related genes, including the transient receptor potential (TRP) channels. Among these genes, TRPA1 exhibited three species-specific amino acid replacements, which differed from those found in infrared imaging snakes, implying different temperature-sensing molecular strategies. Based on laser-heating experiments, the T. baileyi-specific mutations in TRPA1 resulted in an increase in heat-induced opening probability and thermal sensitivity of the ion channels under the same degree of temperature stimulation, which may help the organism respond to temperature changes more quickly. These results provide insight into the genetic mechanisms underpinning the evolution of temperature-sensing strategies in ectotherms as well as genetic evidence of temperature acclimation in this group.

Homogenization based macroscopic model of phase transformations and cyclic plasticity in pearlitic steel

In this contribution macroscopic modeling of phase transformations and mechanical behavior of low alloy steels are developed and investigated. Such modeling is of importance in simulations of transient thermo-mechanical processes which can cause phase transformations, examples from the railway industry include train braking induced frictional heating as well as rail grinding and welding operations. We adopt a modeling approach which includes phase transformation kinetics and individual constitutive models for the phases in combination with different homogenization methods. Algorithmic implementations of the isostrain, isostress and self-consistent homogenization methods are presented and demonstrated in finite element simulations of a laser heating experiment. Stress field results from the different homogenization methods are compared against each other and also against experimental data. The importance of including transformation induced plasticity in the modeling is highlighted, as well as the multi-phase stages of the heating and cooling.

Characterizing major and trace element compositions in fallout melt glass from a near-surface nuclear test

The chemical and isotopic compositions of fallout melt glasses from nuclear tests contain a range of information constraining the physical conditions within the fireball and the mechanisms of fallout formation but historic studies tended to exclude the behavior of stable major and trace elements. Here, we present a large study specifically focused on major and trace element relationships within a population of macroscale fallout samples from a single event. We interpret these data to better constrain how fallout melt glass formation in near surface environments is influenced by that environment and demonstrate how major and trace element abundances can provide useful insights into chemical processes within the fireball.Data confirm that the uranium in the fallout glass population derives from two isotopically distinct endmembers: isotopically enriched uranium (presumably from the weapon), and natural composition uranium that may be a combination of anthropogenic and environmental materials from within the blast zone. The similarity between major and trace element concentrations in fallout and corresponding local soils from the event site confirm the local soils as the most probable source of entrained material into the fireball and the source of carrier material into which the bomb vapor was incorporated. The lack of correlation between major and trace element abundances with size indicates that volatility driven processes, such as condensation from the fireball, do not control the composition of macroscale fallout melt glass.Although the fallout has major and trace element chemical characteristics broadly similar to those of the local, associated soils, some systematic differences are observed between the two populations. Fallout melt glass is depleted in volatile elements such as K, Na, Tl and Pb, consistent with heating to temperatures above ∼1000 °C for 3-10 s. This is supported by the results of laser heating experiments performed on rhyolitic soil at temperatures (1600-2200 °C) and timescales (1-120 s) that are broadly relevant to fallout formation conditions. Relative enrichments of metals such as Cu and Co do not correlate with the abundance of uranium, suggesting that fallout also records input of near field anthropogenic materials. Our observations suggest that major chemical features can be related to processing in the fireball and used to inform the thermal-chemical evolution of the system. Ultimately, these data are consistent with a fallout formation mechanism that involves rapid melting of surface materials to form carrier material melts with minor incorporation of bomb vapor and a degree of volumetric volatile loss due to heating.

Thermo-mechanical simulations of laser heating experiments on UO2

In this paper, a thermo-mechanical model suitable for the interpretation of laser heating experiments simulating the power increasing phase of a RIA transient on UO 2 samples is detailed. The thermal model includes a description of the heat deposition on the sample surface and of the heat transfer within the thickness and radius of the UO 2 sample. The mechanical model describes cracking and crushing of the material depending on the loading mode (tension or compression dominated) and on temperature. The brittle - ductile transition in compression is in particular well reproduced. The parameters fitting is based on available uniaxial compression tests performed at high strain rates and on bending tests performed at moderate strain rates. The application of the mechanical model to annular laser heating experiments led to a good estimation of the crushing and cracking location (near the sample periphery), of the crack orientation (circumferential) and of the beginning of cracking.

Microstructure and properties of additively-manufactured WC-Co microlattices and WC-Cu composites

Liquid ink-printing followed by sintering is used to fabricate WC-Co microlattices and cutting tools. The microstructure of WC-xCo (x=0.5-20 wt.%) is studied for a range of carbide-to-binder ratios and for various sintering temperatures. For 0.5≤Co≤5 wt.%, struts in microlattices exhibit residual porosity due to incomplete densification, even at the highest sintering temperature of 1650 °C. With 10 wt.% Co, fully dense lattice struts are achieved after sintering at 1450 °C for 1 h. For 1450-1650 °C sintering temperatures, the hardness of WC-xCo struts initially increases (due to increasing densification with increased Co) and then gradually decreases (due to an increase of softer Co phase, at near-full density). Finite-element modeling (FEM) shows that the uniaxial elastic deformation of WC-10Co lattices is mostly supported by stretching-dominated vertical columns formed by stacking filaments in a 0/90˚ cross-ply geometry. WC-10Co lattices are infiltrated with Cu at 1300 °C to obtain dense WC-Cu composites, with an internal architecture consisting of a WC-rich lattice and Cu-rich channels, with a high thermal conductivity of 140±7 W/(m·K). Under compression, WC-Cu infiltrated composites are supported by the ductile Cu phase after compressive failure of the internal WC-rich lattice, unlike the WC-Co open lattices which show brittle failure. A cutting tool with an internal WC-Cu lattice architecture is fabricated by 3D WC-Co ink-extrusion printing, sintering, and Cu infiltration. Laser heating experiments and FEM confirm that the 3D-printed/infiltrated/architectured WC-Cu composite cutting tool maintains lower temperatures than a uniform WC-Co tool, for equal heat input at the corner of the tool.

Internal resistive heating of non-metallic samples to 3000K and >60GPa in the diamond anvil cell.

High pressure-temperature experiments provide information on the phase diagrams and physical characteristics of matter at extreme conditions and offer a synthesis pathway for novel materials with useful properties. Experiments recreating the conditions of planetary interiors provide important constraints on the physical properties of constituent phases and are key to developing models of planetary processes and interpreting geophysical observations. The laser-heated diamond anvil cell (DAC) is currently the only technique capable of routinely accessing the Earth's lower-mantle geotherm for experiments on non-metallic samples, but large temperature uncertainties and poor temperature stability limit the accuracy of measured data and prohibits analyses requiring long acquisition times. We have developed a novel internal resistive heating (IRH) technique for the DAC and demonstrate stable heating of non-metallic samples up to 3000K and 64GPa, as confirmed by in situ synchrotron x-ray diffraction and simultaneous spectroradiometric temperature measurement. The temperature generated in our IRH-DAC can be precisely controlled and is extremely stable, with less than 20K variation over several hours without any user intervention, resulting in temperature uncertainties an order of magnitude smaller than those in typical laser-heating experiments. Our IRH-DAC design, with its simple geometry, provides a new and highly accessible tool for investigating materials at extreme conditions. It is well suited for the rapid collection of high-resolution P-V-T data, precise demarcation of phase boundaries, and experiments requiring long acquisition times at high temperature. Our IRH technique is ideally placed to exploit the move toward coherent nano-focused x-ray beams at next-generation synchrotron sources.

Analytical modeling of the heat-affected zone in laser-assisted milling of AerMet100 steel

Compared with conventional milling, laser-assisted milling (LAM) enhances the productivity of difficult-to-cut materials and is a green process due to the elimination of coolant. However, this heat-assisted process may induce a detrimental heat-affected zone (HAZ, generally referred to as phase transformation zone) in the workpiece. This paper presents an analytical model to predict the HAZ produced by laser heating in LAM of AerMet100 steel, in which the size of HAZ is determined by comparing the steady temperature field with the phase transformation temperature of workpiece material. A series of laser heating and LAM experiments are performed to validate the HAZ model. XRD technique is employed to analyze the microstructures in the heated and machined surface layers. Phase compositions and retained austenite content of each specimen are compared with those of the base material. The results indicate that the proposed model is feasible. In addition, the effects of different laser parameters on the HAZ are discussed. The size of the HAZ increases significantly with increasing laser power and decreases significantly with increasing feed speed. The HAZ width increases with the increase of laser spot size, and it appears the opposite change for the HAZ depth. This work can be applied to determine the process parameters in LAM that will yield no residual HAZ in the workpiece after machining.

Constraining the behavior of gallium isotopes during evaporation at extreme temperatures

Renewed interest in gallium isotope systematics has stemmed from the fact that Ga is moderately volatile and is hypothesized to undergo kinetic fractionation during evaporation. Here, we present the first Ga isotope data from terrestrial volatile depleted samples including a suite of experimentally heated rhyolitic soils, fallout melt glass, and splash-form tektites from the Australasian strewn field (hereafter termed australite tektites). The Ga in these samples is isotopically heavy compared to Ga in terrestrial basalts and estimates for the composition of the bulk silicate Earth (BSE). For each sample suite the isotopic fractionation of Ga scales with the degree of Ga depletion, consistent with isotopic fractionation caused by evaporation.The rapid experimental heating of rhyolitic soil to temperatures ranging between 1600 and 2200 °C resulted in volatile loss from the starting soil. Based on the fraction of Ga that was evaporated and the degree of Ga isotopic fractionation between starting soil and experimental samples, we calculate a fractionation factor (α) of 0.99891 ± 0.00024. This is within uncertainty of the fractionation factor we previously calculated for Zn isotopes in the same sample suite (0.99879 ± 0.00013). Although Ga isotopic data from nuclear fallout melt glass is less coherent, the Ga isotope systematics are generally consistent with a suppressed fractionation factor of approximately 0.9995–0.9998 during evaporation, which is also similar to the behavior of Zn systematics. Thus, although the fractionation factors obtained from the laser heating experiments and fallout melt glass are different, in both cases Ga and Zn behave similarly, as evidenced by the covariation of δ71Ga and δ66Zn in these samples.The behavior of Ga isotopes in australite tektites is more difficult to constrain because we do not know the location of the impact site and hence the chemical composition of the target rocks. Nevertheless, based on the composition of more volatile rich Muong-Nong type tektites, we estimate that evaporative fractionation of Ga occurs with an α between 0.9998 and 0.9987; broadly consistent with data from the laser heating experiments and nuclear fallout glass. There is no correlation between δ71Ga and δ66Zn values in australite tektites which is likely to reflect inherited isotopic heterogeneity from weathered precursor material in combination with varying extents of evaporative loss during tektite formation.Gallium isotope ratios in mare basalts are generally isotopically heavy compared to basalts from Earth. Individual mare basalts have δ71Ga and δ66Zn values that do not correlate, contrary to data from the laser levitation experiments and nuclear fallout glass. This suggests that δ71Ga and/or δ66Zn values were fractionated by geologic processes after the Moon had accreted.

In situ characterization of the high pressure \u2013 high temperature melting curve of platinum

In this work, the melting line of platinum has been characterized both experimentally, using synchrotron X-ray diffraction in laser-heated diamond-anvil cells, and theoretically, using ab initio simulations. In the investigated pressure and temperature range (pressure between 10 GPa and 110 GPa and temperature between 300 K and 4800 K), only the face-centered cubic phase of platinum has been observed. The melting points obtained with the two techniques are in good agreement. Furthermore, the obtained results agree and considerably extend the melting line previously obtained in large-volume devices and in one laser-heated diamond-anvil cells experiment, in which the speckle method was used as melting detection technique. The divergence between previous laser-heating experiments is resolved in favor of those experiments reporting the higher melting slope.