"The modern age has a false sense of security because of the great
mass of data at its disposal. But the valid issue is the extent to
which people know how to form and master the material at their disposal."
Illustration of the topological change of the constant energy
surfaces in H 3S Fermi surface. 3S that provides the van Hove singularities
that makes this simple compound the current highest temperature
constant energy surfaces of the new
high temperature superconductor H 3S
as the topological changes occur through the van Hove points.
Our group has performed investigations into the impact of these
van Hove singularities on the properties of H 3S.
Description of the MnO Mott transition from insulator to metal
at one million atmospheres pressure. We extended and applied the
dynamical mean field theory method to obtain the magnetic
and volume collapse transition.
It was found Hund's rule exchange processes are important for
obtaining the correct transformation pressure. Moreover, residual
magnetism was obtained from the calculation, in agreement with
spectroscopic data. The figure provides the current knowledge on
the pressure-temperature phase diagram of MnO.
Dynamics of Superconducting H 3S
In 2004 current theory (China) predicted that hydrogen sulfide
H 33S would become a super-high temperature superconductor at
the very high pressure of 2 million atmosphers. In 2005 Eremets' group in
Germany measured and found the same amazing result. One of our contributions
has been to perform an ab initio molecular dynamics simulation of
atomic vibrations of H3S at a temperature of 200 K and the experimental
pressure. The hydrogen vibration amplitudes are very large; in a
metal with normal (heavy) nuclei, the vibration would hardly be visible.
Note: this video (click the title) may be slow to load.
Fermi surface & Nesting function.
Superconductivity and lattice instability in compressed lithium
from Fermi surface hot spots.
Lithium superconducts up to 20K at high pressure, before
structural phase transitions (lattice instabilities) occur,
limiting higher T c.