scholarly journals Structure and Correlation Between the Fraction of Structural Units and Bond Angle Distribution in Liquid B2 O3 Under Compression

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Pressure Range ◽  
Bond Angle ◽  
Structural Heterogeneity ◽  
Dynamics Simulation ◽  
Angle Distribution ◽  
Structural Units ◽  
Dynamical Heterogeneity ◽  
Heterogeneous Dynamics ◽  
Bond Angle Distribution ◽  
Spatially Heterogeneous Dynamics

Structure of network-forming liquid B2 O3 is investigated by Molecular dynamics simulation (MDS) at 2000K and in the 0-40 GPa pressure range (corresponding to the 1.71-3.04 g/cm3 density range). Results indicate that network structure of liquid B2 O3 comprises of basic structural units BO3 and BO4 . The topology and size of BO3 and BO4 units at different densities are identical. The O-B-O and B-O-B partial bond angle distributions (BADs) can be determined through the fraction of BO3 and BO4 units. Furthermore, the total BADs are directly related to the partial BADs and the fraction of structural units. It means the fraction of units BOX (X = 3,4) and units OBy (y = 2,3) can be determined from the experimental BADs. The spatial distribution of BO3 and BO4 units is not uniform but forming clusters of BO3 and BO4 . This leads to the polyamorphism in liquid B2 O3 . It also shows that the dynamical heterogeneity in liquid B2 O3 due to the lifetimes of BO3 and BO4 units are very different. The structural heterogeneity is origin of spatially heterogeneous dynamics in liquids B2 O3 .

Molecular dynamics simulation for structural heterogeneity and diffusion process in liquid GeO2

2021 ◽  
Vol 66 (1) ◽  
pp. 42-48
Author(s):  
Kien Pham Huu ◽  
Linh Nguyen Hong ◽  
Hien Pham Xuan ◽  
Linh Nguyen Thi Thuy ◽  
Quang Phan Dinh ◽  
...  
Keyword(s):  
Diffusion Process ◽  
Length Distribution ◽  
Structural Heterogeneity ◽  
Dynamics Simulation ◽  
Angle Distribution ◽  
Structural Units ◽  
Oxide Systems ◽  
Dynamical Heterogeneity ◽  
Liquid Oxide ◽  
And Diffusion

In this paper, we perform a simulation about liquid GeO2. The structure and diffusion process are analyzed through the radial distribution function, the distribution of GeOx (x = 4, 5, 6) structural units, length distribution, angle distribution, and data visualization. Simulation results show that the structure of liquid GeO2 composes clusters of GeO4, GeO5, or GeO6. These clusters have sizes depending on pressure and are distributed heterogeneously in space. This result confirms the origin of dynamical heterogeneity in the liquid oxide systems. In addition, the diffusion coefficient of Ge and O decreases upon pressure. We show that the diffusion relates to the breaking bond Ge-O.

THE CORRELATION BETWEEN BOND ANGLE DISTRIBUTION AND THE COORDINATION OF SILICA LIQUID UNDER PRESSURE

2012 ◽  
Vol 26 (20) ◽  
pp. 1250117 ◽  
Author(s):  
L. T. VINH ◽  
N. V. HUY ◽  
P. K. HUNG
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Bond Angle ◽  
Simple Expression ◽  
Dynamics Simulation ◽  
Angle Distribution ◽  
Bond Angle Distribution ◽  
Simulation Results ◽  
Substantial Change ◽  
Good Agreement

Molecular dynamics simulation is carried out for liquid SiO 2 at pressure ranged from zero to 30 GPa and by using BKS, Born–Mayer type and Morse–Stretch potentials. The constructed models reproduce well the experimental data in terms of mean coordination number, bond angle and pair radial distribution function. Furthermore, the density of all samples can be expressed by a linear function of fractions SiO x. It is found that the topology of units SiO x and linkages OSi y is unchanged upon compression although the liquid undergoes substantial change in its network structure. Consequently, the partial bond angle distribution for SiO x and OSi y is identical for all samples constructed by the same potential. This result allows to establishing a simple expression between total bond angle distribution (BAD) and fraction of SiO x and OSi y. The simulation shows a good agreement between the calculation and simulation results for both total O–Si–O and Si–O–Si BADs. This supports a technique to estimate amount of units SiO x and linkages OSi y on base of total Si–O–Si and O–Si–O BADs measured experimentally.

Structure and Properties of the GeAsS Glasses from Ab initio Calculations

2014 ◽  
Vol 1035 ◽  
pp. 502-507
Author(s):  
Li An Chen
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Ab Initio ◽  
Bond Angle ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Angle Distribution ◽  
Structure And Properties ◽  
Bond Angle Distribution ◽  
Pair Distribution Functions

The structure and properties of the GexAsxS100-2x have been studied by ab initio molecular dynamics simulation. By calculating the pair distribution functions, bond angle distribution functions, we analyze the structure and properties of the alloys. Calculations show that Ge and As are all well combined with S atoms. When x is smaller than 25.0 the binding increases with x , when x is larger than 25.0 the binding decreases with increasing x . The intervention of As atom does not affect the GeS2 formation in Ge40As40S80

Molecular Dynamics Simulation of Size Effect on the Mechanical Properties of Amorphous Silica

2015 ◽  
Vol 30 ◽  
pp. 59-67
Author(s):  
Fang Li Duan ◽  
Cheng Zhang ◽  
Qing Song Liu
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Size Effect ◽  
Amorphous Silica ◽  
Bond Angle ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Angle Distribution ◽  
Small Model ◽  
Large Model

The frustules of diatoms have excellent elasticity and high strength, but their main composition, amorphous silica, is a kind of typical brittle material. Molecular dynamics simulations of the uniaxial tension were carried out to study the size effect on the mechanical properties of amorphous silica. Stress-strain behavior, the radius of biggest void, radial distribution functions and bond angle distribution were analyzed. Our results show the small model exhibits a better ultimate strength, ductility and toughness than the large model, and the generation and expansion of voids plays an important role in the fracture behavior of the model. For the small model, some of Si-O bonds are stretched, and the average of O-Si-O bond angle decreases from 108o to 95o, which makes the model have a capability to perform larger plastic deformation and lead to a better ductility. However, for the large model, except the change of Si-O-Si bond angle, its structure has no other significant changes. Our results demonstrate that changes of size have significant impact on the mechanical properties and deformation mechanism of intrinsically brittle materials at the nanoscale.

A MOLECULAR DYNAMICS SIMULATION STUDY OF THE POLYHEDRAL STRUCTURE OF LIQUID ARGON DURING GLASS TRANSITION

2009 ◽  
Vol 23 (08) ◽  
pp. 1069-1075
Author(s):  
CONG LI ◽  
DAN WANG ◽  
JIAYUN LI ◽  
YONGPING DUAN ◽  
MEILI LI ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Glass Transition ◽  
Solidification Process ◽  
Md Simulations ◽  
Liquid Argon ◽  
Dynamics Simulation ◽  
Angle Distribution ◽  
Lennard Jones ◽  
Bond Angle Distribution ◽  
Order Increase

Polyhedron structures changes in Lennard–Jones (LJ) liquid argon containing 108 atoms are investigated by means of molecular dynamics (MD) simulations during the glass transition. The local bond orientational parameter and the bond angle distribution are calculated. In particular, a new parameter is introduced to simultaneously quantify the changes of all the major polyhedral structures: tetrahedron, hexahedron, octahedron, dodecahedron, and icosahedron. The results show that icosahedral order, hexahedral order and octahedral order increase with decreasing temperature, while tetrahedral order and dodecahedral order decrease. This indicates that the glass transition is a solidification process with complex microstructure changes.

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