Plane and plane-radial discrete breathers in fcc metals

Abstract

Discrete breather (DB) is a time-periodic, spatially localized vibrational mode in a perfect nonlinear lattice. In this study, two new types of DBs are reported in fcc metals (Al, Cu and Ni), based on the molecular dynamics simulations using standard embedded atom method interatomic potentials. All calculations are performed at a zero temperature in a three-dimensional computational cell with the use of periodic boundary conditions. A plane DB is excited in a single (111) atomic plane by displacing the atoms from their equilibrium lattice sites according to a specific pattern corresponding to a delocalized vibrational mode in a two-dimensional triangular lattice. This plane DB is delocalized in two dimensions and localized in one dimension, normal to the excited (111) plane. It is shown that in all studied metals the plane DBs have maximal lifetimes of 17–22 ps in the range of initial amplitudes of 0.15–0.30 Å. Herewith the studied mode demonstrates a hard type of nonlinearity, i.e. its frequency increases with amplitude. The second new type of DB is the plane-radial DB obtained by imposing a radial localizing function on the plane DB. This disk-type DB is localized in all three dimensions. The time evolution of the atomic displacement amplitudes and the kinetic energy are studied. The DBs of this type can exist for 9 and 4 ps in Cu and Ni, respectively, and then they decay by dissipating their vibrational energy onto neighboring atoms. The long-lived plane-radial DB in Al is not found.

Effect of the stiffness of interparticle bonds on properties of delocalized nonlinear vibrational modes in an fcc lattice

“…It is important to know the location of the DNVM frequency with respect to the phonon spectrum of the fcc lattice. In particular, DNVMs with frequencies above the phonon band are of interest for the study of DBs [20,25,[29][30][31][32]. In the current work, the frequency spectrum of low-amplitude phonon waves is calculated.…”

“…By now, DNVMs have been studied in various materials, for example, in nonlinear chains [12,[16][17][18][19], carbyne [13], graphene [15,[20][21][22][23], diamond [14], and face-centered cubic (fcc) and body-centered cubic (bcc) metals [17,[24][25][26][27][28]. DNVMs with frequencies outside the phonon band of the lattice can be used for obtaining new types of DBs by superimposing a localizing function [20,25,[29][30][31][32].…”

“…By now, DNVMs have been studied in various materials, for example, in nonlinear chains [12,[16][17][18][19], carbyne [13], graphene [15,[20][21][22][23], diamond [14], and face-centered cubic (fcc) and body-centered cubic (bcc) metals [17,[24][25][26][27][28]. DNVMs with frequencies outside the phonon band of the lattice can be used for obtaining new types of DBs by superimposing a localizing function [20,25,[29][30][31][32]. It has been revealed that DNVMs affect the elastic constants of nonlinear lattices [21,33], and the modulational instability of DNVMs with frequencies outside the phonon band results in the formation of chaotic DBs [29,[34][35][36][37][38][39][40][41][42][43].…”

Effect of discrete breathers on macroscopic properties of the Fermi-Pasta-Ulam chain

“…Using ab initio simulations, the presence of DBs in strained graphene and graphane has been confirmed [36,37]. With the help of molecular dynamics method DBs have been studied in the ionic crystals [38][39][40], lattices with pair-wise potentials [41,42], crystals with covalent bonding [43,44], metals [45][46][47][48][49][50][51], intermetallic compounds [52][53][54][55], carbon and hydrocarbon nanomaterials [56][57][58][59][60][61][62][63][64][65][66][67][68], h-BN [69], and DNA [70][71][72][73].…”

One-component delocalized nonlinear vibrational modes of square lattices

“…DNVMs found for a chain and for a 2D triangular lattice were employed to construct linear and planar DBs in fcc metals [18][19][20]. DNVMs were used to find DBs of new type in monoatomic triangular Morse lattice [21,22], in triangular β-Fermi-Pasta-Ulam-Tsingou (FPUT) lattice [23] and in bcc metals [24].…”