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qmc-lttc/hydrogen.f90

64 lines
1.3 KiB
Fortran

double precision function potential(r)
implicit none
double precision, intent(in) :: r(3)
double precision :: distance
distance = dsqrt( r(1)*r(1) + r(2)*r(2) + r(3)*r(3) )
if (distance > 0.d0) then
potential = -1.d0 / distance
else
stop 'potential at r=0.d0 diverges'
end if
end function potential
double precision function psi(a, r)
implicit none
double precision, intent(in) :: a, r(3)
psi = dexp(-a * dsqrt( r(1)*r(1) + r(2)*r(2) + r(3)*r(3) ))
end function psi
double precision function kinetic(a,r)
implicit none
double precision, intent(in) :: a, r(3)
double precision :: distance
distance = dsqrt( r(1)*r(1) + r(2)*r(2) + r(3)*r(3) )
if (distance > 0.d0) then
kinetic = a * (1.d0 / distance - 0.5d0 * a)
else
stop 'kinetic energy diverges at r=0'
end if
end function kinetic
double precision function e_loc(a,r)
implicit none
double precision, intent(in) :: a, r(3)
double precision, external :: kinetic
double precision, external :: potential
e_loc = kinetic(a,r) + potential(r)
end function e_loc
subroutine drift(a,r,b)
implicit none
double precision, intent(in) :: a, r(3)
double precision, intent(out) :: b(3)
double precision :: ar_inv
ar_inv = -a / dsqrt(r(1)*r(1) + r(2)*r(2) + r(3)*r(3))
b(:) = r(:) * ar_inv
end subroutine drift