# 8.3.15. Chemical Reactions¶

See Setting up Chemical Reaction Cases for information on using these keywords.

## 8.3.15.1. STIFF_CHEMISTRY¶

Data Type: LOGICAL

Flag to use stiff chemistry solver (Direct Integration).

## 8.3.15.2. STIFF_CHEM_MAX_STEPS¶

Data Type: INTEGER

Maximum number of internal steps ODEPACK may use to integrate over the time interval. Leaving this value unspecified permits an unlimited number of steps. The stiff solver reports the number of cells that exceed the number of steps as ‘incomplete’.

## 8.3.15.3. USE_RRATES¶

Data Type: LOGICAL

Flag to use legacy chemical reaction UDFs.

## 8.3.15.4. SPECIES_NAME(PHASE)¶

Data Type: CHARACTER

• $$0 \le Phase \le 10$$

Names of gas and solids phase species as it appears in the materials database. The first NMAX(0) are the names of gas species. The next NMAX(1) are the names of solids phase-1 species, etc.

## 8.3.15.5. NMAX(PHASE)¶

Data Type: INTEGER

• $$0 \le Phase \le 10$$

Number of species in phase m. Note that the gas phase is indicated as m=0.