Origin of the Invar effect in iron-nickel alloys

Article Abstract:

Several theoretical models have been suggested to explain the Invar effect, with the most popular traced back to Weiss, the inventor of the 2gamma-state model. However several experimental observations contradict the 2gamma-state model. Ab initio calculations are presented of the volume dependences of magnetic and thermodynamic properties for a typical Invar system, a random face-centered cubic iron-nickel alloy. The magnetic structure is found to be characterized by a continuous transition from the ferromagnetic state.

Nickel alloys, Iron alloys, Iron-nickel alloys

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Experimental and theoretical identification of a new high-pressure phase of silica

Article Abstract:

Attempts have been made to determine the possible existence of denser silica phases at higher pressures, and several potential post-stishovite phases have been suggested based on observation of crystal structures in chemical analogues of silica. The results of an X-ray diffraction study of silica at high temperatures and pressures of between 68-85 GPa are reported. A new high pressures phase occurred, identified with the help of first-principles total-energy calculations.

Practice, Silica, High pressure research, Silicon dioxide

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The hardest known oxide

Article Abstract:

Research is presented describing the discovery of the hardest known oxide, a cotunnite-structured titanium oxide. The oxide is a new titanium dioxide polymorph in which titanium is nine-coordinated to oxygen in the cotunnite structure, and the phase is synthesized at more than 60 gigapascals and temperatures higher than 1000 K.

Oxides, Titanium dioxide, Hardness, Hardness (Materials)

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