Tetrahedral honeycomb surface reconstructions of quartz, cristobalite and stishovite

Abstract

Crystalline silica (SiO2) is a major material used in many technologies, yet the exact surface structures of silica polymorphs are still mostly unknown. Here we perform a comprehensive study of surface reconstructions of α-cristobalite (001), α-quartz (001) and stishovite (110) and (100) using evolutionary algorithm USPEX in conjunction with ab initio calculations. We found the well-known “dense surface” to be among low-energy reconstructions of α-quartz (001), as well as its previously proposed distorted version, which we call “shifted surface”. For cristobalite and stishovite we show the formation of reconstructions without dangling bonds which share common features with well-known “dense surface” of α-quartz (001). We call them “dense cristobalite” and “dense stishovite” – all of these have honeycomb arrangements of corner-sharing SiO4-tetrahedra in the surface layers. These tetrahedral honeycombs have very low surface energies, and such tetrahedral surface pattern is observed even in stishovite (the bulk structure of which has SiO6-octahedra, rather than SiO4-tetrahedra).

Analysis of individual molecular dynamics snapshots simulating wetting of surfaces using spheroidal geometric constructions

“…To the best of our knowledge the latter and the most stable structure was predicted in 20 . It was then studied in [22][23][24] , with experimental confirmation reported in 22 . As far as the authors of this paper are concerned, there are no reports where the most stable 6-member ellipselike rings pristine (001) α-quartz surface is explicitly mentioned in the context of its wettability or reconstructed using classical molecular dynamics.…”

“…From the hexagonal unit cell of α-quartz 41 shown in Figure 5 Arrangement of the very top atoms of the surface is the same as in the lowest energy surface obtained in [23][24] . The surface consists of 6-member ellipse-like rings, Figure 6.…”

“…To this end we use a water droplet on a pristine (001) -quartz surface in carbon dioxide environment under 4 and 10 MPa pressure and at 300 K temperature. The pristine quartz surface was previously modelled and reconstructed in [20][21][22][23][24] . According to available information in the literature the pristine surface has two energetically very similar structures the 6-member triangle-like rings and the 6member ellipse-like rings.…”

Pembuatan Batubata dengan Bahan Baku Lumpur Sidoarjo

“…Pada gambar 7 diberikan struktur kristal quartz dan crystobalite yang tersusun dari polimer silika oksida (SiO2) (Feya, 2018). Pada gambar tersebut tampak perbedaan struktur kristal keduanya, dimana kristal quartz berbentuk rombik (kubus miring) dengan sudut-sudut yang runcing.…”

“…Gambar 7. Strutur Permukaan Atas Kristal SiO2 (a) Quartz, (b) Crystobalite (Feya, 2018) (Heldar dkk, 2014) menggambarkan proses polimerisasi kristal qwarsa terjadi secara bertahap, dimulai dari unit terkecil yaitu tetrahedral silikat (SiO44-) seperti pada gambar 7. Unit-unit ini kemudian bergabung membentuk tetrahedral ganda dan akhirnya membentuk struktur polyhedral silikat sudut 12.…”