QMCChem

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One of our main activities is the development of the massively parallel QMC code QMC=Chem.

Current Features

Methods

  • VMC
  • DMC
  • Jastrow factor optimization
  • CI coefficients optimization

Wave functions

  • Single determinant
  • Multi-determinant
  • Multi-Jastrow
  • Nuclear cusp correction

Properties

Practical aspects

  • Very low memory requirements
  • Runs on a large number of processors : tested on 512 processors at the CALMIP cluster, and on 1000 processors on the EGEE European grid.
  • Checkpointing
  • Fault tolerant : if the code is aborted, the data is kept. This feature is very useful in grid environments.
  • Easy development with the IRPF90 tool.
  • Variable number of MPI processes during the calculation : can be changed at any time
  • Documentation

Parallel speed-up curve

Qmcchem speedup.png
Number of processors Number of computed blocks Speed-up
1 5 1
8 41 8
16 81 16
32 170 32
64 321 64
128 644 128
256 1280 256
512 2417 483
Number of computed blocks in 140 seconds, where each block is composed of 50 walkers realizing 10,000 VMC steps (water molecule).


Features under development

Properties

  • Molecular Forces
  • Moments (dipole, quadrupole,...)
  • Electron density
  • ZV-ZB EPLF estimator

Practical aspects

  • Graphical interface for input and output


Input file creation

The QMC=Chem input file can be created using the web interface. Upload a Q5Cost file or an output file from GAMESS, Gaussian or Molpro, and you will download the QMC=Chem input directory.

Papers related to the QMC=Chem code