QMCChem

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

• The Electron Pair Localization Function

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
• Fail safe : if the code is aborted, the data is kept. This feature is very useful in grid environments.
• Easy development with the IRPF90 tool.
• Documentation

Parallel speed-up curve

Number of computed blocks in 140 seconds, where each block is composed of 50 walkers realizing 10,000 VMC steps (water molecule).

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

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

• Large-scale quantum Monte Carlo electronic structure calculations on the EGEE grid