Density functional calculations of elastic properties of portlandite, Ca(OH)2

The elastic constants of portlandite, Ca(OH)2, are calculated by use of density functional theory. A lattice optimization of an infinite (periodic boundary conditions) lattice is performed on which strains are applied. The elastic constants are extracted by minimizing Hooke's law of linear elasticity, applying a least-square method. Young's modulus and bulk modulus are calculated from the stiffness matrix. The results are compared with the Brillouin zone spectroscopy results of F. Holuj et al. [F. Holuj, M. Drozdowski, M. Czajkowski, Brillouin spectrum of Ca(OH)2, Solid State Commun., 56 (12) (1985) 1019-1021.]. An error estimate has been performed and the results are compared with experimental values.