Atomic Structure, Electronic and Mechanical Properties of Pyrophyllite under Pressure: A First-Principles Study

Xinzhan Qin,Manchao He,Jiamin Wang,Jian Zhao

doi:10.3390/min10090778

Xinzhan Qin, Manchao He + Show 2 more

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https://doi.org/10.3390/min10090778

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Abstract

Pyrophyllite is extensively used in the high-pressure synthesis industry as a pressure-transmitting medium because of its outstanding pressure transmission, machinability, and insulation. Therefore, the atomic structure, electronic, and mechanical behavior of pyrophyllite [Al4Si8O20(OH)4] under high pressure should be discussed deeply and systematically. In the present paper, the lattice parameters, bond length, the electronic density of states, band structure, elastic constants, and mechanical parameters of pyrophyllite are investigated using density functional theory (DFT) from a microscopic perspective. The pressure dependence of atomic structure, electronic, and mechanical properties of pyrophyllite is analyzed for a wide range of pressure (from 0 GPa to 13.87 GPa). Under high pressure, the major bond lengths and layer thicknesses decrease slightly, and mechanical properties are improved with increasing pressure. The calculated electronic and band structures show only a slight change with increasing pressure, implying that the effect of pressure on the electronic property of pyrophyllite is weak, and pyrophyllite still has good stability under high pressure. The theoretical calculations presented here clarify the electronic and mechanical properties of natural pyrophyllite that are difficult to obtain experimentally because of their small particle size.

Highlights

Pyrophyllite [Al2 Si4 O10 (OH)2 ] is an important non-metallic material commonly used in metallurgy, construction materials, petroleum, chemical and light industry, and other fields because of its good physico-chemical and mechanical characteristics [1]
To better understand the effect of applied pressure on the mechanical properties, we systematically study the elastic properties of pyrophyllite based on density functional theory, including elastic modulus such as the orientation-averaged bulk, shear, and Young’s moduli, as well as the Poisson’s ratios
Pyrophyllite is a planar 2:1 phyllosilicate composed of two-dimensional mineral layers that stack into particles [32]

Summary

Introduction

Pyrophyllite [Al2 Si4 O10 (OH)2 ] is an important non-metallic material commonly used in metallurgy, construction materials, petroleum, chemical and light industry, and other fields because of its good physico-chemical and mechanical characteristics [1]. It is generally known that pyrophyllite is a kind of hydrous aluminosilicate mineral with continuous layered structure. The water is distributed between two silica tetrahedral layers [2], and is linked with aluminum to form an “aluminum hydroxide”. The structural lamellae mainly depend on van der Waals force, and it is easy to slip under the shear action, so it is an ideal pressure-transmission medium. The compact lamellar structure gives pyrophyllite good sealing performance [4]. Pyrophyllite has been widely used in the high-pressure synthesis industry as a sealed pressure-transmission medium

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