CMSP Seminar on Atomistic Simulation Theory Wednesday 27 June at 11am - Stasi - Yosuke KANAI

[CM Section]

Condensed Matter Seminar
Atomistic Simulation Theory Seminar

Wednesday 27 June at 11:00 a.m.
Luigi Stasi Seminar Room, first floor, Leonardo building

Electronic Stopping from Non-Equilibrium Real-Time
TDDFT Simulation: Development and Applications

Yosuke KANAI
Dept. of Chemistry, Univ.of North Carolina at Chapel Hill, USA

Abstract:

I will discuss our recent development of massively-parallel real-time 
time-dependent

density functional theory (RT-TDDFT) method based on the 
planewave-pseudopotential

formalism and its applications to modeling electronic stopping in 
condensed matters.

RT-TDDFT provides a convenient framework for numerically studying 
non-pertubative
electron dynamics coupled with lattice (i.e. ions) movements in large 
systems.
Because of the massively parallel nature of modern high-performance 
computers,
development of new numerical algorithms is often not free from 
considering its parallelizability
over large numbers of processors. We have developed a highly-scalable 
implementation
of RT-TDDFT in qb at ll code for studying large extended systems. We will 
discuss
performance of our new implementation over millions of processor cores, 
reaching
the peta-flops performance. I will then discuss its application to the 
problem of electronic
stopping. Electronic stopping describes the transfer of the kinetic 
energy from a highly-
energetic ion to electrons in condensed matter. The projectile ions bear 
a highly localized
electric field that is quite heterogeneous at the atomistic scale, and 
massive electronic
excitations are produced in the process. Electronic stopping has been 
long studied within
linear response theory framework (e.g. Bethe theory). I will discuss how 
non-equilibrium
simulations based on RT-TDDFT enable us to study this electronic 
excitation process, in
particular for the importance case of liquid water under proton 
irradiation. In addition to
determining the energy transfer rate (i.e. electronic stopping power), 
our work reveals
several key features in the excitation dynamics at the mesoscopic and 
molecular levels
in liquid water under proton irradiation.