Update README.md

Signed-off-by: Fabiana 🚀  Campanari <113218619+FabianaCampanari@users.noreply.github.com>

Author: FabianaCampanari

README.md

@@ -250,6 +250,11 @@ Ramanujan's deep insights into infinite series and modular forms continue to inf
    [Where]():  
      - **\( E \)**: Energy of a state.  
      - **\( \mu \)**: Chemical potential.  
+     - **\( k_B \)**: Boltzmann constant.  
+    
+   
+
+