Added module for integrators

src/MD/MD.jl

@@ -0,0 +1,35 @@
+###
+### "THE BEER-WARE LICENSE":
+### Alberto Ramos wrote this file. As long as you retain this 
+### notice you can do whatever you want with this stuff. If we meet some 
+### day, and you think this stuff is worth it, you can buy me a beer in 
+### return. <alberto.ramos@cern.ch>
+###
+### file:    MD.jl
+### created: Fri Oct  8 21:53:14 2021
+###                               
+
+module MD
+
+# Dalla Brida / Luscher coefficients of
+# fourth order integrator
+const r1 =  0.08398315262876693
+const r2 =  0.25397851084105950
+const r3 =  0.68223653357190910
+const r4 = -0.03230286765269967
+const r5 =  0.5-r1-r3
+const r6 =  1.0-2.0*(r2+r4)
+
+struct IntrScheme{N, T}
+    r::NTuple{N, T}
+    eps::T
+    ns::Int64    
+end
+
+omf4(::Type{T}, eps, ns) where T = IntrScheme{6,T}((r1,r2,r3,r4,r5,r6), eps, ns)
+leapfrog(::Type{T}, eps, ns) where T = IntrScheme{2,T}((0.5,1.0,0.5), eps, ns)
+
+export IntrScheme, omf4, leapfrog
+
+
+end