diff --git a/doc/Eqs/dihedral_charmm.jpg b/doc/Eqs/dihedral_charmm.jpg
index c76994ff23..5ab8a3555c 100644
Binary files a/doc/Eqs/dihedral_charmm.jpg and b/doc/Eqs/dihedral_charmm.jpg differ
diff --git a/doc/Eqs/dihedral_charmm.tex b/doc/Eqs/dihedral_charmm.tex
index 96af7fb52c..c3d860b265 100644
--- a/doc/Eqs/dihedral_charmm.tex
+++ b/doc/Eqs/dihedral_charmm.tex
@@ -3,7 +3,7 @@
 \begin{document}
 
 $$  
-  E = K [ 1 + \cos (n \phi + d) ]
+  E = K [ 1 + \cos (n \phi - d) ]
 $$
 
 \end{document}
\ No newline at end of file