48 lines
848 B
Fortran
48 lines
848 B
Fortran
program linear
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implicit none
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integer :: nelec
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integer :: i,k
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real*8 :: factor
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real*8 :: zpe
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real*8,allocatable :: cmat(:)
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real*8,allocatable :: omega2(:)
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write(6,*) "number of electrons"
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read(5,*) nelec
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allocate (cmat(nelec))
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allocate (omega2(nelec))
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factor=acos(-1d0)/nelec
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cmat = 0d0
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do i = 1, nelec
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cmat(1) = cmat(1) + (1d0 + cos(factor*i))**2/sin(factor*i)**3
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enddo
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do i = 1, nelec-1
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cmat(i+1) = -(1d0 + cos(factor*i))**2/sin(factor*i)**3
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enddo
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cmat = cmat*factor**3/8d0
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factor = 2*acos(-1d0)/nelec
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omega2 = 0d0
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do k = 0, nelec-1
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do i = 0, nelec-1
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omega2(k+1) = omega2(k+1) + cmat(i+1)*cos(factor*k*i)
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enddo
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enddo
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zpe=0d0
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do k = 1, nelec
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if (omega2(k)<0d0) cycle
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zpe = zpe + sqrt(omega2(k))
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enddo
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zpe=zpe/nelec
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print*,'zero-point energy (in Ry and Ha) =',zpe,zpe/2
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deallocate(cmat,omega2)
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end program linear
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