Monthly Archives: January 2011


goal:  to investigate Quantum Monte Carlo
            as a method for Quantum Chemistry

Quantum Chemistry (QC) attempts to predict the reactivity behaviour of atoms and molecules using quantum mechanics. It is also fundamental to molecular physics and molecular biology. QC offers a powerful theoretical tool, especially to the life sciences.

The Schrödinger Equation describes the quantum state of a physical system evolving in time. Solutions of such equations can be used to calculate energy levels, structure, and bonding properties of atoms and molecules. This usually involves tactical approximations and a good deal of calculus.

To take advantage of distributed computing power, the QMC@home project is applying the Quantum Monte Carlo approach. In Monte Carlo analysis, the problem at hand is mapped onto a kind of dartboard. The ‘darts’ are then randomly generated (hence the name Monte Carlo). Many darts (perhaps millions) are thrown onto the map to estimate probabilities. The results are analyzed to provide solutions.

A simple example of Monte Carlo analysis is the calculation of π.
If a circle (radius=r) is placed exactly inside a square (side=2r), the ratio of the area of the circle to that of the square is π/4. Random ‘darts’ thrown at this ‘map’ can be tallied to estimate the same ratio. This is called a Monte Carlo (MC) simulation.
Therefore, π = 4 x (MC ratio). More darts on the MC map will generally lead to a more accurate estimate of π.

QMC is new, and its applicability to real chemistry requires further study. This study requires massive amounts of parallel computing power. This is where the public can help. To join the effort, you need only install a ‘client’ on your PC. This client is a small piece of software that usually runs in the background. Participation in this effort by the general public is free, easy to do, and strongly encouraged.