Grow 2.2 is based upon the original Grow 1.0 suite of programs developed by Meredith Jordan, Keiran Thompson, Ryan Bettens, Alexander Duncan and Michael Collins. A number of significant changes have been made to the original code. The major new features include:

• addition of a Quantum Diffusion Monte Carlo (QDMC) module for calculation of the lowest rovibrational eigenstate of a system
• python scripts to control the growing process, which replace the shell scripts in the original version. This makes the Grow package more robust and gives it greater portability.
• the ability to use the quantum chemistry package Aces2 as a source of ab initio data, in addition to Gaussian. (Note: there is a known bug in the Aces code that calculates numerical second derivatives from first derivatives)
• the ability to interpolate potential energy surfaces from density functional data, using any exchange or correlation functional implemented in Gaussian03
• rearranged (modular) input files
• a second collection of python scripts to control the growing process, designed to function on machines with queuing systems (NQS, PBS). These additions and improvements have been implemented by Deborah Crittenden and Keiran Thompson. As Grow 2.2 is significantly different to Grow 1.0, this user manual is written as stand-alone documentation, and some information from the Grow 1.0 manual may be reproduced here.