Add DL_POLY section

Doc/Src_tex/ScalFmm-PeriodicModel/periodicmodel.tex

@@ -362,10 +362,10 @@ The kernel should be able to proceed usual FMM operator in a tree of height of s
 The energy computed by molecular dynamics codes is given by
 $$
 U = \frac{1}{4 \pi\epsilon_0}\sum_{i=0}^{N}{\sum_{j<i}{\frac{q_i q_j}{\|x_i-x_j\|}}}
-$$
+$$ 
 and the force on atom $x_i$
 $$
-f(x_i) =  \frac{1}{4 \pi\epsilon_0}\sum_{j=0,i\neq j}^{N}{q_j\frac{x_i-x_j}{\|x_i-x_j\|^3}}
+f(x_i) =  \frac{q_i }{4 \pi\epsilon_0}\sum_{j=0,i\neq j}^{N}{q_j\frac{x_i-x_j}{\|x_i-x_j\|^3}}
 $$
 \subsubsection{DL\_Poly comparisons}
 DL\_POLY\_2 uses the following internal molecular units \\
@@ -387,8 +387,8 @@ U = \frac{q_0^2}{4 \pi\epsilon_0 l_0}\sum_{i=0}^{N}{\sum_{j<i}{\frac{q_i q_j}{\|
 $$
 and the forces write 
 $$
-f(x_i) = -\frac{q_0}{4 \pi\epsilon_0 l_0^2}\sum_{j=0,i\neq j}^{N}{q_j\frac{x_i-x_j}{\|x_i-x_j\|^3}}
- = -C_{force}\sum_{j=0,i\neq j}^{N}{q_j\frac{x_i-x_j}{\|x_i-x_j\|^3}}
+f(x_i) = -\frac{q_0^2}{4 \pi\epsilon_0 l_0^2} q_i \sum_{j=0,i\neq j}^{N}{q_j\frac{x_i-x_j}{\|x_i-x_j\|^3}}
+ = -C_{force} q_i  \sum_{j=0,i\neq j}^{N}{q_j\frac{x_i-x_j}{\|x_i-x_j\|^3}}
 $$
 
 The Energy conversion factor is $\gamma_0 = \frac{q_0^2}{4 \pi\epsilon_0 l_0}/E_0 = 138935.4835$. The energy unit is in Joules and if you want $kcal mol^{-1}$ unit the the factor becomes $\gamma_0/418.400$.