r0=1
De=1
ks=100
beta = sqrt(ks/(2*De))

morse(r)=De*(1-exp(-sqrt(ks/(2*De))*(r-r0)))**2
lipp(r)=De*(1-exp(-ks*r0*(r-r0)**2/(2*De*r)))
lm(r)= (r<r0?morse(r):lipp(r)) - De

pt = 2.0
spr = 0.4

hartree = 4.356

q(x) = 0.5 + erf((x-pt)/spr)/2.0
j(x) = q(x)*lipp(x) + (1.0-q(x))*morse(x) - De

#plot [.9:2][-1.1:.1] j(x), (0)

lj(x)=4*(1/x**24-1/x**12)
lj(x)=4*(1/x**32-1/x**16)
lj(x)=175*(1/x**65-1/x**64)
lj2(x,n)=lj((x-1)/n+1)
lj2(x,n)=lj(n*(x-1)+1.0625)
plot [.8:2][-1.1:.2] morse(x)-1,(0),lj2(x,.7),j(x)
plot [.8:2][-1.1:.2] morse(x-.098)-1,(0),lj2(x,6.2),j(x-.098)