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45 lines
1.0 KiB
Fortran
45 lines
1.0 KiB
Fortran
program variance_hydrogen
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implicit none
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double precision, external :: e_loc, psi
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double precision :: x(50), w, delta, energy, dx, r(3), a(6), norm, s2
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double precision :: e, energy2
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integer :: i, k, l, j
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a = (/ 0.1d0, 0.2d0, 0.5d0, 1.d0, 1.5d0, 2.d0 /)
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dx = 10.d0/(size(x)-1)
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do i=1,size(x)
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x(i) = -5.d0 + (i-1)*dx
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end do
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delta = dx**3
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r(:) = 0.d0
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do j=1,size(a)
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energy = 0.d0
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energy2 = 0.d0
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norm = 0.d0
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do i=1,size(x)
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r(1) = x(i)
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do k=1,size(x)
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r(2) = x(k)
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do l=1,size(x)
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r(3) = x(l)
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w = psi(a(j),r)
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w = w * w * delta
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e = e_loc(a(j), r)
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energy = energy + w * e
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energy2 = energy2 + w * e * e
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norm = norm + w
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end do
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end do
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end do
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energy = energy / norm
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energy2 = energy2 / norm
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s2 = energy2 - energy*energy
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print *, 'a = ', a(j), ' E = ', energy, ' s2 = ', s2
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end do
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end program variance_hydrogen
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