Alexander Goncharov

Learn More
Changes in the electronic configuration of iron at high pressures toward a spin-paired state within host minerals ferropericlase and silicate perovskite may directly influence the seismic velocity structure of Earth's lower mantle. We measured the complete elastic tensor of ferropericlase, (Mg(1-x),Fe(x))O (x = 0.06), through the spin transition of iron,(More)
Optical absorption spectra have been measured at pressures up to 80 gigapascals (GPa) for the lower-mantle oxide magnesiowüstite (Mg,Fe)O. Upon reaching the high-spin to low-spin transition of Fe2+ at about 60 GPa, we observed enhanced absorption in the mid- and near-infrared spectral range, whereas absorption in the visible-ultraviolet was reduced. The(More)
Raman spectroscopy in laser-heated diamond anvil cells has been employed to probe the bonding state and phase diagram of dense hydrogen up to 140 GPa and 1,500 K. The measurements were made possible as a result of the development of new techniques for containing and probing the hot, dense fluid, which is of fundamental importance in physics, planetary(More)
N. Arkani-Hamed, J. Bourjaily, F. Cachazo, A. Goncharov, A. Postnikov, and J. Trnka a School of Natural Sciences, Institute for Advanced Study, Princeton, NJ b Department of Physics, Harvard University, Cambridge, MA c Perimeter Institute for Theoretical Physics, Waterloo, Ontario, CA d Department of Mathematics, Yale University, New Haven CT e Department(More)
High P-T Raman measurements of solid and fluid hydrogen to above 1100 K at 70 GPa and to above 650 K in 150 GPa range, conditions previously inaccessible by static compression experiments, provide new insight into the behavior of the material under extreme conditions. The data give a direct measure of the melting curve that extends previous optical(More)
contrast, our work demonstrates a photoinduced liquid motion triggered by azobenzenes immobilized on a solid surface. 15. S.-K. Oh, M. Nakagawa, K. Ichimura, Chem. Lett. 4, 349 (1999). 16. M. Fujimaki et al., Langmuir 14, 4495 (1998). 17. E. Kurita et al., J. Mater. Chem. 8, 397 (1998). 18. Olive oil is a mixture containing fatty acids, vitamins and so on,(More)
Iron in crustal and mantle minerals adopts several possible oxidation states: this has implications for biogeochemical processes, oxygenation of the atmosphere and the oxidation state of the mantle. In the deep Earth, iron in silicate perovskite, (Mg(0.9)Fe(0.1))SiO(3), and ferropericlase, (Mg(0.85)Fe(0.15))O, influences the thermal conductivity of the(More)
Transition metal nitrides are of great technological and fundamental importance because of their strength and durability and because of their useful optical, electronic, and magnetic properties. We have evaluated a recently synthesized platinum nitride (PtN) that was shown to have a large bulk modulus, and we propose a structure that is isostructural with(More)
Raman and infrared spectroscopy of para-H2 to pressures in excess of 200 GPa and to 8 K using new ultrapure synthetic diamond anvils reveals numerous new vibrational excitations in the three highpressure phases. Highly resolved Raman-active librons indicate differences in orientational ordering between phases II and III, including evidence for changes(More)
High-pressure Raman, infrared, x-ray, and neutron studies show that H2 and H2O mixtures crystallize into the sII clathrate structure with an approximate H2/H2O molar ratio of 1:2. The clathrate cages are multiply occupied, with a cluster of two H2 molecules in the small cage and four in the large cage. Substantial softening and splitting of hydrogen vibrons(More)