Challenges in Molecular Dynamics Simulations of Multicomponent Oxide Glasses

Abstract

Despite tremendous progresses made in the past few decades in molecular dynamics simulations of glass and related materials, there exist a number of challenges in MD simulations of multicomponent glasses. This chapter summarizes the progresses in this field and present the challenges that include the reliable and transferable empirical potentials, cooling rate, system size and concentration effect on the simulated glass structures, and the validating structures of multicomponent oxide systems. Several practical examples on multicomponent and technologically important glass systems using classical MD simulations are also given to highlight the capabilities and challenges. IntroductionSince its first application on silica glasses about four decades ago [1-3], molecular dynamics (MD) simulations have become an effective and almost indispensable method in studying the atomic structure and structure-property relationships in glass materials. Glass structure lacks long-range order and defies any single experimental method in structural determination, in contrast to crystalline materials where diffraction method can usually uniquely determine the atomic structures. The structure of glasses is also not random or featureless but, on the contrary, there exist plenty of short-and medium-range structure characteristics that play critical roles on the behaviors and properties of glasses. Determining these glass structure characteristics still poses as a significant challenge in modern characterizations methods and remains a frontier of physical science, although significant progresses in methods such as high energy X-ray and neutron diffraction [4], solid state NMR [5], EXAFS [6], and more recently atom tomography [7]. Atomistic simulations, especially MD based methods, have been playing a more and more important role in investigating

Composite reinforcement: Recent development of continuous glass fibers

“…MD is an atomistic simulation method based on the solution of Newton's equation of motion of an assembly of atoms or molecules that represent the structure of a system, a glass, crystal, or a melt. One of the most important inputs in MD simulations is the empirical interatomic potential; the quality and reliability of the potential to a large extent determine the results and thus the quality of MD simulations . The cooling rate of the simulated glass is typically in the order of 10 12 K/s, significantly higher than that experienced in commercial glass processing (1‐100 K/s) but closer to fiber drawing (10 5−7 K/s).…”

“…In MD simulations of molten glass of the Na 2 O‐CaO‐Al 2 O 3 ‐SiO 2 system, tendency of Na segregation on the melt surface was predicted, implying the existence of higher NBOs near the melt surface over the bulk (Figure ). MD simulations of B 2 O 3 ‐containing glasses pose a more significant challenge, mainly due to the availability of suitable potentials to reproduce effect of composition on boron distribution, [BO 3 ] vs [BO 4 ] . Limited successes were reported so far, but with more recent development of empirical potentials for borosilicate and boroaluminosilicate glasses, it is expected that more compositions close to realistic fiber glasses can be simulated in the near future …”

Structural features of sodium silicate glasses from reactive force field‐based molecular dynamics simulations

“…It was first utilized and refined by Du and Cormack based on original D. M. Teter parameterization to improve the glass structures, for example, cation coordination species and cation‐oxygen bond distance . Further parameters for cation‐oxygen pairs, such as Li–O, Ca–O, Al–O, Zr–O, and P–O, have been developed and tested in various alkali and alkaline earth silicate, aluminate, and phosphate glasses . Recent development on the boron‐related parameters enables this potential set to simulate multicomponent boron‐containing glass compositions with industrial and technological interests, including bio‐active glass and nuclear waste glass …”

Structural role of ZrO2 and its impact on properties of boroaluminosilicate nuclear waste glasses

“…Molecular dynamics (MD) simulation is an effective method of studying structural information in glass materials, and it provides a direct observation of atomic structure, which is difficult to obtain from experimental methods. 25 Many studies have been systematically conducted and revealed shortrange and medium-range structural features utilizing MD simulation in various glass systems such as sodium silicate glasses, 26 aluminosilicate glasses, 27 lithium disilicate glasses, 28 cerium aliminophosphate glasses, 29 europium-doped silicate glasses, 30,31 erbium-doped sodium silicate glasses, 32 lithium vanadophosphate glasses, 33 and bioactive glasses. [34][35][36] However, MD simulation of nuclear waste glasses has been limited due to the lack of pairwise potential sets for boron.…”