  We study a model of phantom tethered membranes, embedded in three-dimensional
space, by extensive Monte Carlo simulations. The membranes have hexagonal
lattice structure where each monomer is interacting with six nearest-neighbors
(NN). Tethering interaction between NN, as well as curvature penalty between NN
triangles are taken into account. This model is new in the sense that NN
interactions are taken into account by a truncated Lennard-Jones potential
including both repulsive and attractive parts. The main result of our study is
that the system undergoes a first-order crumpling transition from low
temperature flat phase to high temperature crumpled phase, in contrast with
early numerical results on models of tethered membranes.
