Hydrogen adsorption is a popular and flexible method
to regulate
the physical properties of two-dimensional (2D) materials, such as
the recently synthesized biphenylene networks. In this study, the
mechanical properties and the thermal conductivity (κ) of a
fully hydrogenated biphenylene network (HBPN) under strain were investigated
systematically by molecular dynamics (MD) simulation and the wave-packet
(WP) propagation method. It was found that HBPN could sustain an unusual
strain as large as 28.8 and 34.5% along the zigzag and armchair directions,
respectively, which were much larger than the other 2D buckling structures
like silicene (about 19.5 and 17%, respectively). Besides, the κ
of HBPN exhibited an anomalous response to the uniaxial tensile strain.
Different from its mother structure, like graphene, the κ of
HBPN had an increasing trend with strain, explained here with the
phononic density of states (PDOS). The physical mechanism behind this
nontrivial thermomechanical behavior of this planar sp2 hybridized carbon allotrope was related to the following two factors:
first, the increase of the number of phonons excited in a low-frequency
region, which in general carried more energy, and second, the reduction
of the number of higher frequency phonons, thus the weakening of the
phonon-surface scattering, both helped increase the thermal conductivity
under strain. Moreover, the strain-induced flattening of the structure
was another reason to weaken the coupling between phonons with in-plane
and curvature vibrational modes. The WP propagation method within
MD was also employed to analyze the propagation of phonons inside
the HBPN, and group velocities, phonon lifetimes, and mean free paths
were obtained. Our research can provide an essential reference for
the application of 2D materials in the field of electronic cooling
devices and the modification of thermoelectric energy conversion efficiency
of materials.