second attempt to fix the latex display

src/10_xray_solutions.md

@@ -148,24 +148,27 @@ $S(\mathbf{G}) = \sum_j f_j e^{i \mathbf{G} \cdot \mathbf{r_j}} = f(1 + e^{i \pi
 
 Solving for $h$, $k$, and $l$ results in 
 
-$
-S(\mathbf{G}) = \begin{cases}
-    2f, \: \mathrm{if\: h+k+l\: is \:even}\\
-    0,  \: \mathrm{if\: h+k+l\: is \:odd}.
+$$
+S(\mathbf{G}) = 
+\begin{cases}
+        2f, \: \mathrm{if\: h+k+l\: is \:even}\\
+        0,  \: \mathrm{if\: h+k+l\: is \:odd}.
 \end{cases}
-$
+$$
+
 Thus if $h+k+l$ is odd, diffraction peaks dissapear
 
 3.
 
 Let $f_1 \neq f_2$, then
 
-$
-S(\mathbf{G}) = \begin{cases}
-    f_1+f_2, \: \mathrm{if\: h+k+l\: is \:even}\\
-    f_1-f_2,  \: \mathrm{if\: h+k+l\: is \:odd}.
+$$
+S(\mathbf{G}) = 
+\begin{cases}
+        f_1+f_2, \: \mathrm{if\: h+k+l\: is \:even}\\
+        f_1-f_2,  \: \mathrm{if\: h+k+l\: is \:odd}.
 \end{cases}
-$
+$$
 
 4.
 Due to bcc systematic absences, the peaks from lowest to largest angle are: