Increasing the division bar length for a fraction in LaTeX math mode

I couldn't find any specific command to increase the length of the division bar when displaying fractions in LaTeX.  My problem was this

\dfrac{\dfrac{\partial^2 C_1}{\partial R^2}}{\dfrac{\partial C_1}{\partial R}}

\[ \dfrac{\dfrac{\partial^2 C_1}{\partial R^2}}{\dfrac{\partial C_1}{\partial R}} \]

So I just manually added some space around the function like this.  You don't have to do it for the bottom (it doesn't work vice versa with the top if you have the space on the bottom).  I just did because I am somewhat OCD, :P.

\dfrac{\hspace{0.25 cm}\dfrac{\partial^2 C_1}{\partial R^2} \hspace{0.25 cm}}{\hspace{0.25 cm} \dfrac{\partial C_1}{\partial R} \hspace{0.25 cm}}

\[ \dfrac{\hspace{0.25 cm}\dfrac{\partial^2 C_1}{\partial R^2} \hspace{0.25 cm}}{\hspace{0.25 cm} \dfrac{\partial C_1}{\partial R} \hspace{0.25 cm}} \]

\dfrac{\hspace{0.25 cm}\dfrac{\partial^2 C_1}{\partial R^2} \hspace{0.25 cm}}{\dfrac{\partial C_1}{\partial R}}

\[ \dfrac{\hspace{0.25 cm}\dfrac{\partial^2 C_1}{\partial R^2} \hspace{0.25 cm}}{\dfrac{\partial C_1}{\partial R}} \]

\dfrac{\dfrac{\partial^2 C_1}{\partial R^2}}{\hspace{0.25 cm} \dfrac{\partial C_1}{\partial R} \hspace{0.25 cm}}

\[ \dfrac{\dfrac{\partial^2 C_1}{\partial R^2}}{\hspace{0.25 cm} \dfrac{\partial C_1}{\partial R} \hspace{0.25 cm}} \]