CPMC-Lab: a MATLAB Package for Constrained Path Monte Carlo Calculations

Authors: Huy Nguyen (lead author), Hao Shi, Jie Xu and Shiwei Zhang.

Citation: Computer Physics Communications, Volume 185, Issue 12, December 2014, Pages 3344-3357

DOI permanent link: 10.1016/j.cpc.2014.08.003. Full text:

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We describe CPMC-Lab, a MATLAB program for the constrained-path and phaseless auxiliary-field Monte Carlo methods. These methods have allowed applications ranging from the study of strongly correlated models, such as the Hubbard model, to ab initio calculations in molecules and solids. The present package implements the full ground-state constrained-path Monte Carlo (CPMC) method in MATLAB with a graphical interface, using the Hubbard model as an example. The package can perform calculations in finite supercells in any dimensions, under periodic or twist boundary conditions. Importance sampling and all other algorithmic details of a total energy calculation are included and illustrated. This open-source tool allows users to experiment with various model and run parameters and visualize the results. It provides a direct and interactive environment to learn the method and study the code with minimal overhead for setup. Furthermore, the package can be easily generalized for auxiliary-field quantum Monte Carlo (AFQMC) calculations in many other models for correlated electron systems, and can serve as a template for developing a production code for AFQMC total energy calculations in real materials. Several illustrative studies are carried out in one- and two-dimensional lattices on total energy, kinetic energy, potential energy, and charge- and spin-gaps.

Passive Optical Separation and Enrichment of Cells by Size Difference

Authors: Siew Kit Hoi, Vuong Hoang Kim, Nguyen Manh Huy, Chorng-Haur Sow, Yueh-Sheng Ow and Andrew Bettiol.

Citation: Biomicrofluidics, Volume 4, Issue 4, December 2010, Pages 044111-044119

DOI permanent link: 10.1063/1.3523057. Full text:

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A size-selective cell sortingmicrofluidic device that utilizes optical force is developed. The device consists of a three-dimensional polydimethylsiloxane microstructure comprised of two crossed microchannels in a three-dimensional configuration. A line shaped focused laser beam is used for automatic size-selective cell sorting in a continuous flow environment. As yeast cells in an aqueous medium are fed continuously into a lower channel, the line shaped focused laser beam is applied (perpendicular to the direction of flow) at the junction of the two crossed channels. The scattering force of the laser beam was employed to push cells matching specific criteria upward from one channel to another. The force depends on the size of the cells, the laser power, and the fluid flow speed. The variation in size of yeast cells causes them to follow different routes at the intersection. For flow speeds below 30 μm/s, all yeast cells larger than 3 μm were removed from the main stream. As a result, a high purity sample of small cells can be collected at the outlet of bottom channel.