The beginnings...

coulomb.hs

type Charge = Double
type Distance = Double
type Force = Double
type Coord = Double
type Mass = Double

data Element = H | O | C deriving (Eq, Show, Read)

data Position = Position { xPos :: Coord
                         , yPos :: Coord
                         , zPos :: Coord
                         } deriving (Eq, Show, Read)

data Atom = Atom { element :: Element
                 , mass :: Mass
                 , charge :: Charge
                 , position :: Position
                 } deriving (Eq, Show, Read)

k_e = 8.987551787368176e10

class Dist a where
    (<->) :: a -> a -> Distance

instance Dist Position where
    (<->) x y = sqrt sumOfSquares
            where sumOfSquares = xs ** 2 + ys ** 2 + zs ** 2
                  xs           = xPos x - xPos y
                  ys           = yPos x - yPos y
                  zs           = zPos x - zPos y

instance Dist Atom where
    (<->) x y = position x <-> position y

electrostatic :: Atom -> Atom -> Force
electrostatic a1 a2 = coulomb c1 c2 d
            where c1 = charge a1
                  c2 = charge a2
                  d  = a1 <-> a2

coulomb :: Charge -> Charge -> Distance -> Force
coulomb q1 q2 r = k_e * q1 * q2 / (r ** 2)