isosteric heat in MS

Dear all,

i have one doubt.  Material studio gives output on  basis of eq. 1(as you mention,https://community.accelrys.com/message/6284#6284). as disussed in  "Isosteric heat in MS sorption".Which  means that at higher loading,  output of isosteric heat from Material  studio is wrong? because assumption related to neglecting adsobate  volume(Va) is not vallid assumption at heigher loading.

is it? please clarify my doubt.

Thanks

Amar