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1.
We determined the phase diagram involving diamond, graphite, and liquid carbon using a recently developed semiempirical potential. Using accurate free-energy calculations, we computed the solid-solid and solid-liquid phase boundaries for pressures and temperatures up to 400 GPa and 12 000 K, respectively. The graphite-diamond transition line that we computed is in good agreement with experimental data, confirming the accuracy of the employed empirical potential. On the basis of the computed slope of the graphite melting line, we rule out the hotly debated liquid-liquid phase transition of carbon. Our simulations allow us to give accurate estimates of the location of the diamond melting curve and of the graphite-diamond-liquid triple point. 相似文献
2.
Haverkort MW Hu Z Tanaka A Ghiringhelli G Roth H Cwik M Lorenz T Schüssler-Langeheine C Streltsov SV Mylnikova AS Anisimov VI de Nadai C Brookes NB Hsieh HH Lin HJ Chen CT Mizokawa T Taguchi Y Tokura Y Khomskii DI Tjeng LH 《Physical review letters》2005,94(5):056401
Utilizing a sum rule in a spin-resolved photoelectron spectroscopic experiment with circularly polarized light, we show that the orbital moment in LaTiO3 is strongly reduced from its ionic value, both below and above the Ne el temperature. Using Ti L2,3 x-ray absorption spectroscopy as a local probe, we found that the crystal-field splitting in the t2g subshell is about 0.12-0.30 eV. This large splitting does not facilitate the formation of an orbital liquid. 相似文献
3.
Braicovich L Ghiringhelli G Tagliaferri A van der Laan G Annese E Brookes NB 《Physical review letters》2005,95(26):267402
We present measurements of the magnetic circular dichroism in x-ray resonant emission in the perpendicular geometry (circularly polarized x rays at normal incidence to the magnetization) for L(2,3) the absorption region in Fe, Co, and Ni metal. The results show that spin-dependent screening of the core hole takes place within the scattering time scale, which is supported by the absence of the effect in ionic systems. This allows an assessment of the time scale for the screening process (up to a few femtoseconds). The process is almost complete within the scattering time for Fe and Co, but this is not the case for the narrow band metal Ni which shows a much slower dynamics. 相似文献
4.
Bonfim M Ghiringhelli G Montaigne F Pizzini S Brookes NB Petroff F Vogel J Camarero J Fontaine A 《Physical review letters》2001,86(16):3646-3649
We have developed a new original technique to study the magnetization reversal dynamics of thin films with element selectivity in the nanosecond time scale. X-ray magnetic circular dichroism measurements in pump-probe mode are carried out taking advantage of the time structure of synchrotron radiation. The dynamics of the magnetization reversal of each of the layers of complex heterostructures (like spin valves or tunnel junctions) can be probed independently. The interlayer coupling in the studied systems has been shown to play a key role in the determination of the magnetization reversal of each individual layer. 相似文献
5.
A two-dimensional steady-sate analysis of semi-infinite brittlecrack growth at a constant subcritical rate in an unboundedfully-coupled thermoelastic solid under mixed-mode thermomechanicalloading is made. The loading consists of normal and shear tractionsand heat fluxes applied as point sources (line loads in theout-of-plane direction). A related problem is solved exactly in an integral transformspace, and robust asymptotic forms used to reduce the originalproblem to a set of integral equations. The equations are partiallycoupled and exhibit operators of both Cauchy and Abel types,yet can be solved analytically. The temperature change field at a distance from the moving crackedge is then constructed, and its dominant term is found tobe controlled by the imposed heat fluxes. The role of this termis, indeed, enhanced if the heat fluxes serve to render thecrack as a net heat source/sink for the solid, as opposed tobeing a transmitter of heat across its plane. More generally,the influence of the thermoelastic coupling on this field, aswell as other functions, is found to increase with crack speed. 相似文献
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7.
K. Kummer A. Tamborrino A. Amorese M. Minola L. Braicovich N. B. Brookes G. Ghiringhelli 《Journal of synchrotron radiation》2017,24(2):531-536
A software with a graphical user interface has been developed with the aim of facilitating the data analysis for users of a new resonant inelastic X‐ray scattering (RIXS) spectrometer installed at the ESRF beamline ID32. The software is organized in modules covering all relevant steps in the data reduction from a stack of several hundred two‐dimensional CCD images to a single RIXS spectrum. It utilizes both full charge integration and single‐photon centroiding to cope with high‐flux and high‐resolution requirements. Additional modules for further data analysis and the extraction of instrumental parameters are available. The software has been in routine use for about a year now and in that time many additional features have been incorporated. It now meets the users' need for an easy‐to‐use data analysis tool that allows looking at and understanding data as it is acquired and thus steering users' experiments more efficiently. 相似文献
8.
G. Ghiringhelli A. Piazzalunga X. Wang A. Bendounan H. Berger F. Bottegoni N. Christensen C. Dallera M. Grioni J.-C. Grivel M. Moretti Sala L. Patthey J. Schlappa T. Schmitt V. Strocov L. Braicovich 《The European physical journal. Special topics》2009,169(1):199-205
Resonant inelastic x-ray scattering in the soft x-ray
regime has been profiting much from technical advances that have
lowered considerably the instru- mental linewidth. At the ADRESS beam
line of the Swiss Light Source the SAXES spectrometer can be used to
measure RIXS spectra at the L edges of the 3d transition metals
with unprecedented energy resolution, of the order of 100 meV for
Mn, Ni and Cu. We present here some preliminary spectra on CuO,
malachite, NiO, NiCl2, MnO and LaMnO3. The dd excitations
are very well resolved allowing accurate experimental evaluation of
3d state energy splitting. The low energy scale becomes
accessible opening the way to the study of collective excitations in
strongly correlated electron systems, like magnons and orbitons. 相似文献
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10.
We report a Car-Parrinello molecular dynamics study of the liquid-liquid phase transition in phosphorus. We employed a gradient corrected density functional (B-LYP) to describe the electronic structure and performed simulations at constant pressure. Upon increasing pressure we observed, along the 1500 K isotherm, a structural transition converting the molecular P4 liquid into an atomic liquid with a network structure. Our calculations suggest this transition to be first order with a discontinuous density increase accompanied by an insulator into metal transition. The transition pressure is significantly higher than obtained by employing the less accurate local density functional (LDA) [Morishita, Phys. Rev. Lett. 87, 105701 (2001)], which matches the experimental value for the pressure. We argue why the LDA result should be considered fortuitous. The change of the calculated structure factor upon the transition shows the same trend as experimentally observed. Analysis of the structural changes during the phase transition revealed that a chain of linked and opened up ("butterfly") P4 molecules may serve as a seed triggering the transition from the molecular to the network phase. 相似文献