Physicists¹ have predicted that under the influence of sufficiently² high electric fields, liquid droplets⁴（液滴） of certain materials will undergo solidification⁵, forming crystallites at temperature and pressure conditions that correspond to liquid droplets at field-free conditions. This electric-field-induced phase transformation⁶ is termed electrocrystallization. The study, performed by scientists at the Georgia Institute of Technology, appears online and is scheduled as a feature and cover article in the 42nd issue of Volume 115 of the Journal of Physical Chemistry C.

"We show that with a strong electric field, you can induce a phase transition without altering the thermodynamic（热力学的） parameters," said Uzi Landman, Regents' and Institute Professor in the School of Physics, F.E. Callaway Chair and director of the Center for Computational Materials Science (CCMS) at Georgia Tech.

In these simulations, Landman and Senior Research Scientists David Luedtke and Jianping Gao at the CCMS set out first to explore a phenomenon described by Sir Geoffrey Ingram Taylor in 1964 in the course of his study of the effect of lightning on raindrops, expressed as changes in the shape of liquid drops when passing through an electric field. While liquid drops under field-free conditions are spherical⁷（球形的） , they alter their shape in response to an applied⁸ electric field to become needle-like liquid drops. Instead of the water droplets used in the almost decade-old laboratory experiments of Taylor, the Georgia Tech researchers focused their theoretical study on a 10 nanometer (nm) diameter liquid droplet³ of formamide（甲酰胺） , which is a material made of small polar molecules¹⁰ each characterized by a dipole moment that is more than twice as large as that of a water molecule⁹.

With the use of molecular¹¹ dynamics¹² simulations developed at the CCMS, which allow scientists to track the evolution of materials systems with ultra-high resolution in space and time, the physicists explored the response of the formamide nano-droplet to an applied electric field of variable strength. Influenced by a field of less than 0.5V/nm, the spherical droplet elongated¹³ only slightly. However, when the strength of the field was raised to a critical value close to 0.5 V/nm, the simulated droplet was found to undergo a shape transition resulting in a needle-like liquid droplet with its long axis¹⁴ -- oriented along the direction of the applied field -- measuring about 12 times larger than the perpendicular¹⁵ (cross-sectional) small axis（轴） of the needle-like droplet. The value of the critical field found in the simulations agrees well with the prediction obtained almost half a decade ago by Taylor from general macroscopic（宏观的） considerations.

Past the shape transition further increase of the applied electric field yielded a slow, gradual increase of the aspect ratio between the long and short axes of the needle-like droplet, with the formamide molecules exhibiting liquid diffusional motions.