Mechanical Properties of Pristine and Defective Carbon-Phosphide Monolayers: A Density Functional Tight-Binding Study

TL;DR

This study uses density functional tight-binding theory to analyze the elastic, deformation, and failure behaviors of pristine and defective carbon-phosphide monolayers, revealing significant mechanical anisotropy and vacancy effects relevant for nanoelectromechanical applications.

Contribution

It provides the first detailed analysis of the mechanical properties of defective carbon-phosphide monolayers, highlighting vacancy impacts and anisotropic failure mechanisms.

Findings

Carbon monovacancies have the lowest formation energy.

Young's modulus and failure stress are much higher along ZZ direction.

Vacancies significantly affect mechanical properties, especially along AC direction.

Abstract

Using density functional tight-binding theory, we investigated the elastic properties and deformation and failure behaviors of pristine and defective carbon-phosphide (CP) monolayers subjected to uniform uniaxial tensile strain along armchair (AC) and zigzag (ZZ) directions. Two variants of carbon phosphide were studied and two types of carbon and phosphorous vacancies (single and double) were considered. It was found that carbon monovacancies have the lowest formation energy, while phosphorous divacancies have the highest one in both CP allotropes. A strong mechanical anisotropy for carbon phosphide was found with the Young\'s modulus and the failure stress along ZZ direction being an order of magnitude larger than those along AC direction. In both allotropes, the Youngs modulus, failure stress and strain are considerably affected by vacancies, especially along AC direction. Fracture of pristine CP monolayer occurred via the rupture of phosphorous-phosphorous bonds when CP monolayer is stretched along AC direction, while via the rupture of carbon-phosphorous bonds when stretched along ZZ direction. The failure strain and stress along the AC direction are affected only by phosphorous vacancies, while along the ZZ direction, they are almost equally affected by both phosphorous and carbon vacancies. These understandings may provide useful guidelines for potential applications of CP monolayers in nanoelectromechanical systems.