  In 1919 Einstein tried to solve the problem of the structure of matter by
assuming that the elementary particles are held together solely by
gravitational forces. In addition, Einstein also assumed the presence inside
matter of electromagnetic interactions. Einstein showed that the cosmological
constant can be interpreted as an integration constant, and that the energy
content of the Universe should consist of 25\% gravitational energy, and 75\%
electromagnetic energy. In the present paper we reinterpret Einstein's
elementary particle theory as a vector type dark energy model, by assuming a
gravitational action containing a linear combination of the Ricci scalar and
the trace of the matter energy-momentum tensor, as well as a massive
self-interacting vector type dark energy field, coupled with the matter
current. Since in this model the matter energy-momentum tensor is not
conserved, we interpret these equations from the point of view of the
thermodynamics of open systems as describing matter creation from the
gravitational field. In the vacuum case the model admits a de Sitter type
solution. The cosmological parameters, including Hubble function, deceleration
parameter, matter energy density are obtained as a function of the redshift by
using analytical and numerical techniques, and for different values of the
model parameters. For all considered cases the Universe experiences an
accelerating expansion, ending with a de Sitter type evolution.
