Introduction to RMG

RMG is an automatic chemical reaction mechanism generator that constructs kinetic models composed of elementary chemical reaction steps using a general understanding of how molecules react. The model parameters (rate constants and reaction thermodynamics) are estimated using a database and the idea that the behavior of functional groups is somewhat independent of the molecule(s) containing them. The RMG database consists of two parts: kinetic rate rules and thermodynamic group additivity values.

RMG is an object-oriented program written in Java, which provides a stable, robust programming architecture that is easily extended, modified, and improved. At its core, RMG relies on two fundamental data structures: graphs and trees. The graphs represent the chemical structures, and the trees represent the databases of thermodynamic and kinetic data. Currently, RMG can generate reaction mechanisms for species involving carbon, hydrogen, and oxygen, and its mechanisms can contain many hundreds of species and tens of thousands of reactions. It is also capable of performing first-order sensitivity analysis on the rate constants and species thermodynamics.

RMG was originally developed by Dr. Jing Song under the guidance of Prof. William Green in the Department of Chemical Engineering at the Massachusetts Institute of Technology. Currently there are several members of the Green group contributing to RMG’s ongoing development. A full list of past and present RMG developers can be found on the Credits page.

Changes

Changes in RMG 3.2 include the following:

• The RMG_Database folder has been restructured more logically. (PrimaryReactionLibrary and Seed Mechanism specifications in condition files will need updating)
• It is possible to specify forbidden structures in the input file.
• Various error messages have been improved to give more helpful information to the user.

Changes made in RMG 3.1 include the following:

• PrimaryReactionLibrary and PrimaryThermoLibrary now both behave as reference libraries from which data are taken (in preference to group additivity estimates), when and if the data are needed.

• Seed Mechanism allows the mechanism building to start from a seed mechanism, which is included in its entirety before the simulation starts. (This is how PrimaryReactionLibrary behaved in previous releases.)

• New databases: GRIMech 3.0 and PrIMe-recommended thermodynamic values are included

• Support for Chemkin’s P-Log format for k(T,P) reporting (in addition to Chebyshev format).

• Added additional options for the input file, including:

  • User-specified limits for number of carbon / oxygen / radical per species
  • User-specified Chebyshev fitting options

• Changed many dependent Fortran codes to use standard input and output, rather than writing temporary files to disk.

• Reduced run-to-run variations by standardizing the order of averaging of values in the kinetics trees.

Bug Fixes:

• Corrected inconsistencies in edge flux evaluation for pressure-dependent reactions.
• Corrected an error in inert gas normalization for runs with multiple temperatures/pressures
• Fixed DASPK interface
• Fixed bugs in peroxide (ROOR) frequency estimation
• Fixed a bug in the gauche correction database for alkenes
• Fixed issues with duplicate reactions and with Chebyshev fitting in writing CHEMKIN input files
• More frequent garbage collection

Changes made in RMG 3.0 include the following:

New features:

• Pressure-dependent reaction network generation
• InChI generation
• Graphical user interface for input file generation
• Generation of reaction mechanisms for multiple reaction conditions (T,P)
• Automatic time stepping option
• Updated RMG Viewer and Editor (including database editing tools)

Functionality changes:

• On the first step of mechanism generation, only one species is added, rather than adding all edge species
• Thermodynamics estimates for non-cyclic species incorporate certain steric effects (1,5-interactions and gauche interactions)

Bug fixes:

• Fixed bug in symmetry number generation (previously could be underestimated in certain cases)
• Fixed differential equations to correctly treat cases where total number of moles changes