  We present results of \textit{ab initio} molecular dynamics study of a
structural transformation occurring in hot liquid sulfur under high pressure,
which corresponds to the chain-breakage phenomenon recently observed
experimentally by Liu \textit{et al.} [1] and to the electronic transition
reported by Brazhkin \textit{et al.} [2,3]. We performed an extensive
\textit{ab initio} study and confirmed the existence of one transformation
separating two distinct liquid polymeric phases: one composed of short
chain-like fragments and another one with very long chains. We have not
observed additional transformations reported in Refs. [2,3] and in the recent
theoretical study by Zhao and Mu [4] and our findings are in agreement with the
most recent experiment [1]. We offer a structural description of this
liquid-liquid transformation in terms of chain lengths, cross-linking and
geometry and investigate several physical properties. We conclude that the
transformation is accompanied by changes in configurational energy and entropy
as well as in diffusion coefficient and electronic properties
(semiconductor-metal transition), but no density discontinuity was found. We
also describe analogy of the investigated phenomenon to similar processes
present in two other chalcogenes selenium and tellurium. Finally, we discuss
possibility of a critical point terminating the studied transition in relation
to the long-known behavior of ambient-pressure heated sulfur melt.
