Molecular dynamics simulations of the mechanical properties of monoclinic hydroxyapatite

Inorganic biomedical materials are of great interest in the biomedical field. One such material, hydroxyapatite (HAP), is the main inorganic substance in the hard tissue of bones and teeth in the human body. Until recently, studies of the mechanical properties of HAP by uniaxial tension testing and compression molecular dynamics (MD) simulation had remained difficult. In addition, electric charges used in such simulations alter the molecular structure of HAP. Here, we present the mechanical properties and new charges of the monoclinic form of HAP using the self-consistent charge equilibration (QEq) scheme proposed by Rappé and Goddard in 1991 (J Phys Chem 95:3358-3363), and a successful MD simulation of the uniaxially tensile and compressive properties of monoclinic HAP. Also presented is the change in potential energy in the cell and how temperature and strain rate affect the uniaxial tension and compressive properties of HAP. Additionally, we compare the mechanical properties of this substance along different directions, and some conclusions useful for further studies of the mechanical properties of HAP composite materials are discussed.