The generalized identification of truly interfacial molecules (ITIM) algorithm for nonplanar interfaces

Abstract

We present a generalized version of the ITIM algorithm for the identification of interfacial molecules, which is able to treat arbitrarily shaped interfaces. The algorithm exploits the similarities between the concept of probe sphere used in ITIM and the circumsphere criterion used in the α-shapes approach, and can be regarded either as a reference-frame independent version of the former, or as an extended version of the latter that includes the atomic excluded volume. The new algorithm is applied to compute the intrinsic orientational order parameters of water around a dodecylphosphocholine and a cholic acid micelle in aqueous environment, and to the identification of solvent-reachable sites in four model structures for soot. The additional algorithm introduced for the calculation of intrinsic density profiles in arbitrary geometries proved to be extremely useful also for planar interfaces, as it allows to solve the paradox of smeared intrinsic profiles far from the interface.

Intrinsic Structure of the Interface of Partially Miscible Fluids: An Application to Ionic Liquids

“…It is worth mentioning that the ITIM method has recently been generalized to be able to deal with surfaces of arbitrarily curved shapes. 63 …”

Properties of the intrinsic surface of liquid acetone, as seen from computer simulations

“…Since then, following the pioneering work of Chacón and Tarazona [49] a number of methods that are able to locate the intrinsic surface have been proposed [43,[49][50][51][52][53][54][55], among which the Identification of the Truly Interfacial Molecules (ITIM) [43] turned out to be an excellent compromise between computational cost and accuracy [54]. In the ITIM analysis spherical test particles of appropriate size are moved from the bulk opposite phase to the surface along a set of test lines perpendicular to the macroscopic plane of the surface.…”

Properties of the Liquid–Vapor Interface of Acetone–Water Mixtures. A Computer Simulation and ITIM Analysis Study

“…47 Following the pioneering paper of Chacón and Tarazona, 48 several methods have been proposed to circumvent this problem and to detect the real, capillary wave corrugated, intrinsic liquid surface. 41,[49][50][51][52][53][54] Among them, the method of Identification of the Truly Interfacial Molecules (ITIM) 41 turned out to be an excellent compromise between computational cost and accuracy. 53 In an ITIM analysis probe spheres of a given radius are moved along test lines perpendicular to the macroscopic plane of the interface from the bulk opposite phase towards the surface of the phase of interest.…”