  Infrared dark clouds (IRDCs) have dense elongated clumps and filaments with
the favorable viewing condition of being on the near-side of a bright
mid-infrared background. The clumps usually have multiple cores around the
center. In this work, we study the effect of magnetic field morphology on the
structure of massive IRDC clumps. To achieve this goal, we consider an
axisymmetric isothermal oblate IRDC clump, embedded into a constant external
magnetic field. We assume a polynomial function for the magnetic field
morphology inside the clump. We use the numerical iterative methods to solve
the equations: the successive over-relaxation method to find the magnetic and
gravitational fluxes, and then the bicongugate gradient method to find the
optimized values of mass and current densities. The results show that the IRDC
clump will be very elongated along the perpendicular direction of the external
magnetic field lines. Also, the assumption of choosing of a polynomial function
for the magnetic field morphology leads to the formation of dense regions
around the center. The greater the density of the central region, the larger
the density of these dense regions and the closer to the center. The presence
of these dense regions can lead to the formation of cores at these points.
