Calculation of energy relaxation rates of fast particles by phonons in crystals

Abstract

We present ab initio calculations of the temperature-dependent exchange of energy between a classical charged point-particle and the phonons of a crystalline material. The phonons, which are computed using density functional perturbation theory (DFPT) methods, interact with the moving particle via the Coulomb interaction between the density induced in the material by phonon excitation and the charge of the classical particle. Energy relaxation rates are computed using timedependent perturbation theory. The method, which is applicable wherever DFPT is, is illustrated with results for CsI, an important scintillator whose performance is affected by electron thermalization. We discuss the influence of the form assumed for quasiparticle dispersion on theoretical estimates of electron cooling rates.

Coupled rate and transport equations modeling proportionality of light yield in high-energy electron tracks: CsI at 295 K and 100 K; CsI:Tl at 295 K

“…The use of pulsed lasers to measure transient behavior in the picosecond regime 8 and to induce specific ionization densities allowing measurement of nonlinear processes at carrier densities found in the gamma ray induced electron tracks 9 is another. There has been commensurate progress in the theoretical understanding of energy deposition and subsequent transport and recombination along the ionized tracks [10][11][12][13][14][15][16][17][18] .…”

Electron-phonon scattering rates in complex polar crystals

“…In Ref. 21 we formulated a semi-classical theory of the electron-phonon interaction. This theory was derived from a viewpoint complementary to the standard, fully quantum formulation of the electron-phonon interaction [30][31][32][33][34][35] in which the fundamental quantity is the coupling g k,k ′ = k ′ |H ep |k between electronic quasiparticle states |k and |k ′ .…”

“…The integrals are completed numerically using techniques described in Ref. 21 and below. These results then provide an average picture of the scattering that can be parameterized in simplified microscopic models such as KMC simulations: Γ (±) determines how often the particles scatter, and cos θ and ω λ,q determine how fast the propagation direction and speed respectively relax.…”

“…In an effort to direct searches for improved scintillators and shed light on these questions, we have recently developed a semi-classical theory 21 to estimate the rate of energy transfer between hot electrons produced in the cascade initiated by the absorption or Compton scattering of a gamma-ray photon. In the present manuscript we describe refinements to this theory that improve the accuracy and computational feasibility of the method.…”

First-principles search for efficient activators for LaI3

“…Therefore, advances in the fundamental physics of the complex solid-state phenomena that lead to the emission of scintillation photons are expected to translate directly to science-based performance improvements [1]. This realization has driven significant and recent efforts in developing a better understanding of the condensed matter physics of these materials [2][3][4][5][6][7]. In particular, ever-improving software and hardware capabilities have open the door for first-principles calculations to take a more prominent role in material engineering for improved scintillation performance.…”