modify scalarTransportFoam, problems need help
 

Dear all.
I want to modify the salarTransportFoam to solve another problems.The code like this:
fvScalarMatrix VaEqn
(
- fvm::laplacian(Per, Va)
==
F*(Z1*C1+Z2*C2)
);

The fvSchemes file like this:
ddtSchemes
{
default Euler;
}

gradSchemes
{
default Gauss linear;
}

divSchemes
{
default Gauss linear;
}

laplacianSchemes
{
default none;
laplacian(Per, Va) Gauss linear corrected;

}

interpolationSchemes
{
default linear;
}

snGradSchemes
{
default corrected;
}

when runing ,it displayed the following mistake:
"ill defined primitiveEntry starting at keyword 'laplacian(Per,' on line 36 and ending at line 57"
From function void Foam::primitiveEntry::readEntry(const Foam::dictionary&, Foam::Istream&)
in file db/dictionary/primitiveEntry/primitiveEntryIO.C at line 189.
I need help very much. Thank you very much.