Glossary for the OpenChem Workbench.

default molecule property
For some molecule properties which have multiplicity (e.g., names) one is considered by the system to be the default. Note the default is user-selectable.

equilibrium product set
The set of all molecules that are allowed to form in an equilibrium calculation.

fundamental property
(of a molecule) These are properties any of which will differentiate two molecules.

(of a reaction) These are properties any of which will differentiate two reactions.

A polyvalent atom (ligancy >=2) in a molecule, together with all its ligands (Benson, 1976).

a set of rate parameters and a specified thermset.

A chemical species defined by its fundamental properties and including other properties and references. See the Molecule property data format table.

molecule set
A collection of molecules.

molecular weight
Molecular weight of a molecule is always calculated from the user-supplied atomic weights unless the natural abundance flag is set, in which case the atomic weights in the database are used.

natural abundance flag
A flag on a molecule indicating that all the atomic weights of the molecule are assumed to be given by natural abundance. See molecular weight.

pressure-dependent or "third body" reactions
Reactions for which the rate constant depends explicitly on the pressure or equivalently the concentration of "M", the "third body". Unimolecular decomposition reactions of this type are often called "fall-off" reactions. Bimolecular reactions of this type are often called "chemically activated". See for a complete description of the types of pressure-dependent reaction models handled in the OpenChem Workbench.

primary name
(of a molecule) See specifier.

A project consists of a collection of user-defined groups of streams, a collection of user-defined groups of runs, and some annotations.

pseudo-frequency cp fit
A thermodynamic fit of gas phase heat capacity for a molecule, assuming that translational and external rotation modes are fully activated. The vibrational modes are approximated by three frequencies, and three mode degeneracies.

rate constant
A parameter that, when multiplied by the driving force, determines the rate of disappearance of the reactants. The rate constant is a function of temperature and (sometimes) pressure. The functional form is usually modified Arrhenius (k = A T^n exp(-Ea/RT)), however more complicated expressions are used for pressure-dependent reactions (see for details). The driving force is typically the product of the reactant concentrations raised to the power of their stoichiometric coefficients.

ratio of reaction rate constants
The average of the ratios of reaction rates calculated from two different rate constants at three temperatures. If a ratio is less than unity, it is defined as the reciprocal of itself. So, a ratio of reaction rate constants will be always larger or equal to unity. The temperatures are starting temperature, ending temperature and middle temperature of the overlap of the valid temperature range of the two reaction rate constants.

Defined by a group of reactant molecules, a group of product molecules, and their respective stoichiometric coefficients. Often expressed in the form:

aA + bB + ... <-> qQ + rR + ...

The reaction is typically stoichiometrically balanced, but in special cases, unbalanced reactions will be allowed if the "balanced" stoichiometric flag is set to false (e.g., MW growth reactions where tracking hydrogen is not useful or desired).

reaction rate
An equation describing the rate at which a chemical reaction occurs in units of mol vol^-1 time^-1.

reaction set
A collection of reactions.

reverse rate constant
Rate constant describing the rate at which products form reactants.

A combination of temperature, pressure, flow rate, and molar composition of molecular species present.

For a molecule, a unique name for the molecule in the database.

A polynomial thermodynamic fit; i.e., thermodynamic data for a molecule. A molecule may have no or many thermfits.

Short for "thermodynamic set". A collection of user-defined groups of thermfits. Each thermfit corresponds to a unique molecule, so that a molecule is represented only once within a thermodynamic set.

Last modified $Date: 2003/12/23 20:47:14 $ -07:00:00/06:00:00 MDT/MST