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SUMMARY:Electronic response to ion projectiles traversing matter from firs
 t principles - Prof. Emilio Artacho (Cambridge &amp\; Nanogune)
DTSTART:20251009T130000Z
DTEND:20251009T143000Z
UID:TALK232561@talks.cam.ac.uk
CONTACT:Bo Peng
DESCRIPTION:Projectile particles slow down when traversing matter by excit
 ing its electrons. This electronic stopping process has been target of res
 earch throughout the last century motivated by its importance in radiation
  damage in various contexts\, mostly in nuclear and aerospace technologies
 \, but also in medical physics. Linear response methods have been very muc
 h used since Lindhard contributions in the fifties\, given the fact that t
 he effect of such projectiles can be weak if swift enough. They are howeve
 r not suitable for projectile velocities comparable to those of the target
  electrons\, where the energy can transfer at rates from eV per Angstrom t
 o keV per Angstrom\, in a quite strongly out of equilibrium dynamics. The 
 first non-linear theory was proposed at TCM in 1981 for the homogeneous el
 ectron liquid. The radiation damage problem in the synthetic rocks propose
 d for nuclear waste encapsulation prompted our facing the problem for insu
 lators two decades ago. We did it by explicit simulation from first princi
 ples: put a projectile particle in a box containing a big enough sample of
  the material of interest\, start moving it\, and follow the dynamics of t
 he surrounding electrons. The evolution of the energy offers the electroni
 c stopping power\, comparable with experiments\, which allow validation of
  the simulation. We use real-time propagation within time-dependent densit
 y-functional theory. Validation has been satisfactory enough in various sy
 stems so as to take the simulations with some credibility. The described v
 irtual experiments have allowed us to gain deeper understanding of electro
 nic stopping processes\, which has also allowed for furthering the theory 
 in this context. Various results will be presented\, as well as theoretica
 l developments prompted by technical issues (e. g. a moving basis set in t
 he calculations induces a gauge field related the curvature of the wave-fu
 nction manifold\, analogous to Berry’s)\, and a Floquet theory of stoppi
 ng for crystalline systems. 
LOCATION:Seminar Room 3\, RDC
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