  This paper presents a novel 3-D full electromagnetic particle-in-cell (PIC)
code called JefiPIC, which uses Jefimenko's equations as the electromagnetic
(EM) field solver through a full-space integration method. Leveraging the power
of state-of-the-art graphic processing units (GPUs), we have made the
challenging integral task of PIC simulations achievable. Our proposed code
offers several advantages by utilizing the integral method. Firstly, it offers
a natural solution for modeling non-neutral plasmas without the need for
pre-processing such as solving Poisson's equation. Secondly, it eliminates the
requirement for designing elaborate boundary layers to absorb fields and
particles. Thirdly, it maintains the stability of the plasma simulation
regardless of the time step chosen. Lastly, it does not require strict
charge-conservation particle-to-grid apportionment techniques or electric field
divergence amendment algorithms, which are commonly used in finite-difference
time-domain (FDTD)-based PIC simulations. To validate the accuracy and
advantages of our code, we compared the evolutions of particles and fields in
different plasma systems simulated by three other codes. Our results
demonstrate that the combination of Jefimenko's equations and the PIC method
can produce accurate particle distributions and EM fields in open-boundary
plasma systems. Additionally, our code is able to accomplish these computations
within an acceptable execution time. This study highlights the effectiveness
and efficiency of JefiPIC, showing its potential for advancing plasma
simulations.
