  Low-mass X-ray binaries (LMXBs) have a wide range of X-ray properties which
can be utilised to reveal many physical conditions of the associated accretion
discs. We use the spectral synthesis code CLOUDY to perform a detailed
modelling of neutron star LMXBs GX 13+1, MXB 1659--298, 4U 1323--62 and XB
1916--053; and characterise the underlying physical conditions, such as
density, radiation field, metallicity, wind velocity, etc. For this purpose we
model highly ionised spectra of Fe, Ca, S, Si, Mg, Al in the soft X-ray band,
and compare the predicted line flux ratios with the observed values. We also
find that the strength and profile of these spectral lines get modified in the
presence of magnetic field in the accretion disc. Using this, we estimate an
upper limit of the existing magnetic field to be about a few hundred to a few
thousand G in the accretion discs of these four LMXBs.
