An efficient way to model complex magnetite: Assessment of SCC-DFTB against DFT

Abstract

Magnetite has attracted increasing attention in recent years due to its promising and diverse applications in biomedicine. Theoretical modelling can play an important role in understanding magnetite-based nanomaterials at the atomic scale for a deeper insight into the experimental observations. However, calculations based on density functional theory (DFT) are too costly for realistically large models of magnetite nanoparticles. Classical force field methods are very fast but lack of precision and of the description of electronic effects. Therefore, a cheap and efficient quantum mechanical simulation method with comparable accuracy than DFT is highly desired. Here, a less computational demanding DFT-based method, i.e. self-consistent charge density functional tight-binding (SCC-DFTB), is adopted to investigate magnetite bulk and low-index (001) surface with newly proposed parameters for Fe-O interactions. We report that SCC-DFTB with on-site Coulomb correction provides results in quantitatively comparable agreement with those obtained by DFT+U and hybrid functional methods. Therefore, SCC-DFTB is valued as an efficient and reliable method for the description magnetite. This assessment will promote SCC-DFTB computational studies on magnetite-based nanostructures that attract increasing attention for medical applications.

Multiscale simulations of the hydration shells surrounding spherical Fe3O4nanoparticles and effect on magnetic properties

“…SCC-DFTB, which is a method cheaper and faster than DFT, can well describe Fe 3 O 4 bulk, surface, NPs and the water/Fe 3 O 4 interfaces. 27,31,32 The SCC-DFTB method [36][37][38] is an approximated DFT-based method that derives from the second-order expansion of the Kohn-Sham total energy in DFT with respect to the electron density fluctuations. The SCC-DFTB total energy can be defined as:…”

“…For the Fe-O interactions, we used the Slater-Koster files fitted by some of us previously, 31 which can well describe Fe 3 O 4 bulk, surface, NPs and the water/Fe 3 O 4 interfaces. 27,31,32 SCC-DFTB+U 41 with an effective U − J value of 3.5 eV was adopted to properly deal with the strong correlation effects among Fe 3d electrons, according to our previous work on magnetite. 26,30,32 The convergence criterion of 10 −4 a.u.…”

“… 39 The “trans3d-0-1” set of parameters 40 are used for the Fe–Fe and Fe–H interactions, and the “mio-1-1” set of parameters 36 are used for the O–O, H–O and H–H interactions. For the Fe–O interactions, we used the Slater–Koster files fitted by some of us previously, 31 which can well describe Fe 3 O 4 bulk, surface, NPs and the water/Fe 3 O 4 interfaces. 27,31,32 SCC-DFTB+U 41 with an effective U − J value of 3.5 eV was adopted to properly deal with the strong correlation effects among Fe 3d electrons, according to our previous work on magnetite.…”

“…Recently, through the development of new Fe-O interaction parameters, we managed to well describe magnetite by the Hubbard corrected self-consistent charge density functional tight-binding (SCC-DFTB+U; from now on, DFTB+U) method, which is a cheap and efficient quantum mechanical simulation method with comparable accuracy to DFT. 31 Then, by combining DFTB+U and hybrid DFT methods, we finally succeeded in the quantum mechanical simulation of Fe 3 O 4 NPs of realistic size (about 2.5 nm) and different shapes under vacuum. 32 In the present study, we have first investigated the adsorption behavior of one isolated water molecule on the Fe 3 O 4 NP surface by putting one water molecule in contact with the bare roundish Fe 3 O 4 NPs from our previous work.…”

Study on crystallization process of SiO2 based SiO2-Li2O nano-wire glass ceramic: A molecular dynamics simulation based on SCC-DFTB calculations

“…The extended tight-binding with self-consistent charge (SCC-DFTB) approach based on quantum mechanical methodology is a DFT-based method regarding to the electron density fluctuations [13,14]. The set of parameters QUASINANO2013.1 [15] available in the Amsterdam Density Functional (ADF) library is utilized for single point calculations of molecules [16][17][18].…”