Problem with subscript in thermodynamic problem

You made four different errors in your sheet:
[ol 1]
[li]Your range variables are going from 1 to 3, but Prime numbers vector elements beginning with the value of the system variable ORIGIN - in your case from 0 to 2[/li]
[li]You define vectors (3x1 matrices) at the top of your sheet and later you try to use these vectors to create a 3x3 matrix with the same name! You can't use the same name for two different structures at the same time.[/li]
[li]You used the literal index (CTRL + -) where you should have used the vector/matrix index ([). You can't address vector elements with an literal index as this is just part of the variables name.[/li]
[li]In the definition of the matrices Vc and Pc you forgot the indices on the LHS of the definition[/li]
[/ol]
Furthermore I noticed that the vector Pc you define at the top is never used in your sheet but is overwritten later by the definition of a matrix Pc. Not sure if that was done on purpose.

Find attached a sheet which fixes all those errors and makes use of range variables independent of the value of ORIGIN. I deleted your global definition of ORIGIN as the default value is 0 anyway and I renamed you various vectors at the top by adding an underline so we don't get into troubles by defining the matrices with the same value.

Thank you very much for the correction, had not noticed that kind of features in mathcad. Thanks for your time and corredigo document.