Slides

QM/MM: CPMD/GROMOS
• Long-­‐range:
• Computed approximately by expanding the charge density of the QM
system in terms of mul4poles up to quadrupolar order:
QM −MM
E es−lr
⎧
⎪ C
= ∑ q I ⎨
R I
− R +
I ∉NN
⎩⎪
+ 1 2
∑
i, j
Q ij
R I
− R 5
• Coefficients C, D i , Q ij are the usual mul4pole moments computed from the
charge density n(r) of the QM subsystem with respect to the geometric
center of the QM system, R = (R 1
, R 2
, R 3
),
where i=1,2,3 are the cartesian
components.
∑
i
• Refinement: third region between the other two:
• Charge density approximately represented by (restraint) electrosta4c
poten4al-­‐based (R/ESP) charges centered on the QM atoms as
obtained from a dynamical fi~ng procedure or taken from the MM
force field used.
A. Laio, J. VandeVondele, U. Röthlisberger J. Chem. Phys. 2002, 116, 6941.
D i
R I
− R 3
( R Ii
− R ) i
( R Ii
− R )( i
R Ij
− R ) j
⎫
⎪
⎬
⎭⎪