  One novel family of two-dimensional IV-V compounds have been proposed, whose
dynamical stabilities and electronic properties have been systematically
investigated using the density functional theory. Extending from our previous
work, two phases of carbon phosphorus bilayers \alpha- and \beta-C$_{2}$P$_{2}$
have been proposed. Both of them are dynamically stable and thermally stable at
300K. They possess intrinsic HSE gaps of 2.70 eV and 2.67 eV, respectively.
Similar \alpha- and \beta-C$_{2}$Y$_{2}$ (Y= As, Sb, and Bi) can be obtained if
the phosphorus atoms in the \alpha- and \beta-C$_{2}$P$_{2}$ replaced by other
pnictogens, respectively. If the C atoms in the \alpha- and
\beta-C$_{2}$Y$_{2}$ (Y= P, As, Sb, and Bi) are further replaced by other IV
elements X (X=Si, Ge, Sn, and Pb), respectively, more derivatives of \alpha-
and \beta-X$_{2}$Y$_{2}$ (Y=N, P, As, Sb, and Bi) also can be obtained. It was
found that the majority of them are dynamically stable. The proposed compounds
range from metal to insulators depending on their constitutions. All insulated
compounds can undergo a transition from insulator to metal induced by biaxial
strain. Some of them can undergo a transition from indirect band gap to direct
band gap. These new compounds can become candidates as photovoltaic device,
thermoelectric material field as well as lamellated superconductors.
