Cheng Shao

Cheng Shao

I am a researcher working on nanoscale electron and phonon transport

Posts by Category

blog

phonon focusing

1 minute read

Published:

Phonon scattering at interfaces

jekyll

Welcome to Jekyll!

less than 1 minute read

Published:

You’ll find this post in your _posts directory. Go ahead and edit it and re-build the site to see your changes. You can rebuild the site in many different ways, but the most common way is to run jekyll serve, which launches a web server and auto-regenerates your site when a file is updated.

research

Experimental techniques for nanoscale thermal measurement

less than 1 minute read

Published:

Some review article on this topic

Vibration modes in amorphous materials

1 minute read

Published:

vibrations in amorphous materials

While in crystals heat is carried by propagating lattice waves, or phonons, in amorphous solids heat carriers are classified as propagons, diffusions, and locons depending on the degree of delocalization of the atomic vibration and its mean free path 12.

  1. P. B. Allen, J. L. Feldman, J. Fabian, and F. Wooten, Philosophical Magazine B 79, 1715(1999). ↩

  2. J. L. Feldman, M. D. Kluge, P. B. Allen, and F. Wooten, Physical Review B 48, 12589 (1993) ↩

Integration Algorithm in Molecular Dynamics Simulaitons

less than 1 minute read

Published:

Integration Algorithm

  • reference
  • The computational effort required is a major consideration in choosing which algorithm to use.
  • An algorithm that is normally more expensive (for example, requires more than one force evaluation per iteration) may permit a significantly longer time step to be used and so, in fact, may be more cost-effective.
  • One of the most important considerations is the energy conservation.
    • a variation of one part in 10^4 is generally considered acceptable.

Lammps modification

less than 1 minute read

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This year I have done a project to investigate the thermal properties of an rigid body system. In this project, we need to predict the thermal conductivity of this system through the Green-Kubo formula. From the paper by Evans at 1976, the exchange of heat flux due to the rotation of molecules need be to considered in the heat flux formula. However, we cannot access to the pairwise torque between molecules in LAMMPS right now. Therefore, I need to make some modification in Lammps to access the rotational degee-of-freedom information and get the correct heat flux information.

The man who trusted atoms

less than 1 minute read

Published:

  • Quantum particle do not have uniquely specific locations or velocities, and collectionos of them must, strictly speaking, be treated as a holistic (“entangled”) whole, rather than as a collection of individuals each of which has a state on its own. (foreword)
  • The distinction between a continuous field and a collection of individual particles is by no means as clear as it was in the classical picture.

switch off the intramolecular nonbonded interaction

less than 1 minute read

Published:

When I running some simulations on ionic liqudis, I realize that may need to turn off the intramolecular nonbonding interactions. Here are some commands in LAMMPS that can do the jobs:

  • night_modify exclude molecule/intra all
  • special_bonds lj/coul 0 0 0

tutorial on IEEE nano 2017 conference

less than 1 minute read

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The IEEE nano conference is held at pittsburgh, so we attend the one day tutorial on nanoscale heat transfer.

Second thought on the Green-Kubo fomular

less than 1 minute read

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  • The key thing is the microscopic expreesion for the heat flux
  • The heat curret is defined as the time derivative of the sum of the moments of the site energies.

Mechine learning: 01

4 minute read

Published:

  • The problem of searching for patterns in data is fundamental one and has a long and successful history.
  • The field of pattern recognition is concerned with the automatic discovery of regularities in data through the use of computer algorithms and with the use of these regularities to take action such as classifying the data into different categories.
  • In mechine learning, a training set is used to tune the parameters of an adaptive model.
  • In most applications, the original training sets are preprocessed to transform them into some new space of variables where, it is hoped, the pattern recognition problem will be easier to solve
    • this pre-processing stage is sometimes also called feature extraction.

update

Welcome to Jekyll!

less than 1 minute read

Published:

You’ll find this post in your _posts directory. Go ahead and edit it and re-build the site to see your changes. You can rebuild the site in many different ways, but the most common way is to run jekyll serve, which launches a web server and auto-regenerates your site when a file is updated.