14 research outputs found
Direct simulation Monte Carlo schemes for Coulomb interactions in plasmas
We consider the development of Monte Carlo schemes for molecules with Coulomb
interactions. We generalize the classic algorithms of Bird and Nanbu-Babovsky
for rarefied gas dynamics to the Coulomb case thanks to the approximation
introduced by Bobylev and Nanbu (Theory of collision algorithms for gases and
plasmas based on the Boltzmann equation and the Landau-Fokker-Planck equation,
Physical Review E, Vol. 61, 2000). Thus, instead of considering the original
Boltzmann collision operator, the schemes are constructed through the use of an
approximated Boltzmann operator. With the above choice larger time steps are
possible in simulations; moreover the expensive acceptance-rejection procedure
for collisions is avoided and every particle collides. Error analysis and
comparisons with the original Bobylev-Nanbu (BN) scheme are performed. The
numerical results show agreement with the theoretical convergence rate of the
approximated Boltzmann operator and the better performance of Bird-type schemes
with respect to the original scheme
The challenges in guided self-assembly of Ge and InAs quantum dots on Si
The topic of guided self-assembly of Ge and InAs quantum dots on Si (001) substrates via epitaxy is discussed. A buried misfit dislocation network can be used to guide the assembly process through the associated strain field. Patterned substrates can also be used to guide the assembly process. This paper discusses the recent experimental and theoretical studies of the guided assembly process with an emphasis on what remains to be understood. (c) 2005 Elsevier B.V. All rights reserved