The calculation of the vibrational frequencies of crystalline compounds and its implementation in the CRYSTAL code

• DOI: 10.1002/jcc.20019
• Publication Date: 2004-03-04T15:00:30Z
• Authors: F. Pascale; C. M. Zicovich‐Wi...; F. López Gejo; B. Civalleri; R. Orlando; R. Dovesi
• Keywords: Hessian matrix; Numerical differentiation; Matrix (chemical analysis)

The problem of numerical accuracy in the calculation vibrational frequencies crystalline compounds from hessian matrix is discussed with reference to alpha-quartz (SiO(2)) as a case study and specific implementation CRYSTAL code. Hessian obtained by differentiation analytical gradient energy respect atomic positions. process calculating involves two steps: determination equilibrium geometry, themselves. parameters controlling truncation Coulomb exchange series Hartree-Fock, quality grid used for integration Exchange-correlation potential Density Functional Theory, SCF convergence criteria, optimization well those can influence some extent. effect all these documented. It concluded that relatively economical computational conditions uncertainty related smaller than 2-4 cm(-1). In Local Approximation scheme, comparison possible recent calculations performed Perturbation Theory method plane-wave basis set.