c6mekl is a multitemperature mekal model using sixthorder Chebyshev polynomial for the differential emission measure. The DEM is not constrained to be positive.. The switch parameter determines whether the mekal code will be run to calculate the model spectrum for each temperature or whether the model spectrum will be interpolated from a precalculated table. The former is slower but more accurate. The reference for this model is Singh et al. (1996, ApJ, 456, 766).
c6pmekl differs by using the exponential of the 6^{th} order Chebyshev polynomial
c6mekl and c6pmekl use abundances relative to the Solar abundances set by the abund command
The variants c6vmkl and c6pvmkl with polynomial and exponential polynomial respectively allow the user to specify 14 elemental abundance.
For c6mekl and c6pmkl the parameters are:
par16 
Chebyshev polynomial coefficients 
par7 
H density (cm^{3}) 
par8 
abundance wrt to Solar 
par9 
Redshift 
par10 
0 calculate 
1 interpolate 

2 interpolate using APEC model 

norm 
Normalization 
While for c6vmkl and c6vpmkl the parameters are:
par16 
Chebyshev polynomial coefficients 
par7 
H density (cm^{3}) 
par821 
Abundances of He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command) 
par22 
Redshift 
par23 
0 calculate 
1 interpolate 

2 interpolate using APEC model 

norm 
Normalization 