Merge pull request castep-docs#143 from Inker2401/xc_typo_fix

Corrected a few typos and added warning for XC_DEFINITION usage

Author: jryates

docs/documentation/Groundstate/population_analysis.md

@@ -60,7 +60,7 @@ is calculated, where $Z'$ is the pseudoatom nuclear charge.
 ### The CASTEP implementation
 
 In CASTEP, the solution of the electronic problem results in a set of Kohn-Sham orbitals $\psi _ i$, which are expressed in terms of plane-wave functions. Plane-waves are non-local, therefore not
-directly suitable for Mulliken population analysis. In order to obtain a suitable local basis, CASTEP solves the electronic problem of the isolated atom for each atomic specie present in the system,
+directly suitable for Mulliken population analysis. In order to obtain a suitable local basis, CASTEP solves the electronic problem of the isolated atom for each atomic species present in the system,
 resulting in a set of atomic orbitals $\chi _ \mu$. Note that for this set of calculations, the same calculation settings (e.g. electronic cutoff and pseudopotentials) are used. With the atomic
 orbitals determined, the Mulliken population analysis can be performed by calculating the projections $\langle \chi _ \mu | \psi _ i \rangle$.
 

docs/documentation/XC/XC.md

@@ -71,9 +71,15 @@ LDA-C 1.0
 %endblock xc_definition
 ```
 
+!!! warning
+	When specifying parameters within the `xc_definition` block, one should not
+	specify separator characters such `:` or `=` between the keyword and parameters.
+	In addition, note that functional names within XC definition are **case-sensitive**
+	and should thus be entered in uppercase.
+
 Examples:  
 1. B3LYP
-Firstly you cansimply use `xc_functional : B3LYP`, however
+Firstly you can simply use `xc_functional : B3LYP`, however
 `B3LYP` is a hybrid functional consisting of a mixture of
 Hartree-Fock, LDA and B88 exchange, LYP and LDA correlation. This
 functional can be specified component by component: