What is Sym8?
Sym8 is a geochemical equilibrium and kinetic modeling package comprising two components:
- Sym8.EQ: Equilibrium chemical speciation
- Sym8.BK: Batch-type open and closed system time-dependent kinetic reactions modeling
The goal of Sym8 is the same as other speciation programs: compute the distribution of dissolved species in water given a set of elemental composition and thermodynamic data.
What distinguishes Sym8 is its mathematical approach, user interface design, and how the database is utilized.
The methodology used in Sym8 programs eliminates the basis species concept entirely. Instead, the user selects a set of elements and Sym8 assembles the complete complement of solutes and complexes from the thermodynamic database. The full set of equilibrium reactions and mass-balance conditions is then assembled into one mathematical system and solved simultaneously.
Sym8 uses a Newton–Raphson method to solve the complete chemical system simultaneously. The Jacobian matrix includes terms for every solute and every mass-balance condition. There is no separation between primary and secondary species, no reduced subsystem, and no basis swapping.
This means the Jacobian is larger than in traditional models, but modern computing handles that comfortably. In return, the system is mathematically simpler and more direct: one convergence criterion, one solve, no iterative coupling between subsystems.
The methodology used in Sym8 programs eliminates the basis species concept entirely. Instead, the user selects a set of elements and Sym8 assembles the complete complement of solutes and complexes from the thermodynamic database. The full set of equilibrium reactions and mass-balance conditions is then assembled into one mathematical system and solved simultaneously.
Sym8 uses a Newton–Raphson method to solve the complete chemical system simultaneously. The Jacobian matrix includes terms for every solute and every mass-balance condition. There is no separation between primary and secondary species, no reduced subsystem, and no basis swapping.
This means the Jacobian is larger than in traditional models, but modern computing handles that comfortably. In return, the system is mathematically simpler and more direct: one convergence criterion, one solve, no iterative coupling between subsystems.
Traditional Models (EQ3/6, GWB, PHREEQC, MINTEQ, etc.)
Traditional speciation programs use a basis species framework
Traditional speciation programs use a basis species framework
- A reduced set of primary (basis) species, one per chemical element
- All secondary species (complexes) are expressed algebraically as functions of the basis species
- The solver works on reduced NxN system, where N is the number of basis species
- The Jacobian (of Newton-Raphson numerical method) contains terms only for the basis species
- Secondary species are calculated from basis species concentrations
Sym8
Sym8 methodology eliminates the basis species concept entirely
Sym8 methodology eliminates the basis species concept entirely
- Solutes are collected from database based on list of chemical elements selected for the chemical system
- All reactions and mass-balance conditions are assembled into one mathematical system
- The solver works on the complete NxN chemical system, where N is the number of solute species