  The presence of supermassive black holes (SMBHs) of a few billion solar
masses at very high redshift has motivated us to study how these massive
objects formed during the first billion years after the Big Bang. The most
promising model that has been proposed to explain this is the direct collapse
of protogalactic gas clouds. In this scenario, very high accretion rates are
needed to form massive objects early on and the suppression of $\mathrm H_2$
cooling is important in regulating the fragmentation. Recent studies have shown
that if we use a strong radiation background, the hydrogen molecules are
destroyed, favoring the high accretion rates and therefore producing objects of
very high mass. In this work we study the impact of UV radiation fields in a
primordial gas cloud using the recently coupled code GRADSPH-KROME for the
modeling of gravitational collapse including primordial chemistry to explore
the fragmentation in AU scales and hence the formation of first SMBHs. We found
that to suppress the formation of $\mathrm H_2$ a very high value of $J_{21}$
is required, because of that we conclude that the direct collapse black holes
(DCBHs) are very unlikely to be an explanation for the formation of the first
SMBHs.
