Static and dynamic structure and the atomic dynamics of liquid Ge from first-principles molecular-dynamics simulations

S. Munejiri, Tadahiko Masaki, T. Itami, F. Shimojo, K. Hoshino

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The first-principles molecular-dynamics simulation was performed for liquid Ge at 1253 K by using two kinds of simulation cells: The cubic cell of 64 atoms and the rectangular parallelepiped one of 128 atoms. The rectangular parallelepiped cell of 128 atoms was adopted to obtain the dynamic structure factor of liquid Ge in the small wave number region. The long simulation time was adopted, i.e., 66 ps for the cubic cell and 75 ps for the rectangular parallelepiped one. The present first-principles molecular-dynamics simulation reproduces well the experimental static structure factor and radial distribution function. A broad peak around 100° in the obtained bond angle distribution function implies the existence of the tetrahedral atomic unit in liquid Ge. The self-diffusion coefficient for the rectangular parallelepiped cell is 20% larger than that of the cubic one. The obtained dynamic structure factor agrees well with the experimental one obtained by the inelastic x-ray scattering experiment, which shows the "de Gennes narrowing" of the main peak and the existence of the side peaks. These side peaks represent a longitudinal vibrational motion, which was also supported by the subsidiary peak around 30 ps-1 in the spectral density of the velocity autocorrelation function. The gradient of the dispersion relation in the present simulation agrees well with the experimental sound velocity. This "no positive dispersion" accords well with the inelastic x-ray scattering experiment of Hosokawa The reason for this "no positive dispersion" for liquid Ge is discussed in particular concern with its low kinematic viscosity. Though the velocity autocorrelation function itself does not show a cage effect, a microscopic cage effect can be found by the detailed analysis for the trace and environment of the single atomic motion. The atomic movement as a group of 3-5 atoms seems to be present in liquid Ge in addition to individual atomic motions. The covalent bond seems to be also present at least instantaneously in liquid Ge.

Original languageEnglish
Article number014206
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume77
Issue number1
DOIs
Publication statusPublished - 2008 Jan 18

Fingerprint

Molecular dynamics
parallelepipeds
molecular dynamics
Computer simulation
Liquids
liquids
cells
Atoms
simulation
x ray scattering
Autocorrelation
autocorrelation
Distribution functions
atoms
inelastic scattering
distribution functions
Scattering
X rays
subsidiaries
Covalent bonds

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Static and dynamic structure and the atomic dynamics of liquid Ge from first-principles molecular-dynamics simulations. / Munejiri, S.; Masaki, Tadahiko; Itami, T.; Shimojo, F.; Hoshino, K.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 77, No. 1, 014206, 18.01.2008.

Research output: Contribution to journalArticle

@article{220e848e91244b9fbf4cd8deea2a143e,
title = "Static and dynamic structure and the atomic dynamics of liquid Ge from first-principles molecular-dynamics simulations",
abstract = "The first-principles molecular-dynamics simulation was performed for liquid Ge at 1253 K by using two kinds of simulation cells: The cubic cell of 64 atoms and the rectangular parallelepiped one of 128 atoms. The rectangular parallelepiped cell of 128 atoms was adopted to obtain the dynamic structure factor of liquid Ge in the small wave number region. The long simulation time was adopted, i.e., 66 ps for the cubic cell and 75 ps for the rectangular parallelepiped one. The present first-principles molecular-dynamics simulation reproduces well the experimental static structure factor and radial distribution function. A broad peak around 100° in the obtained bond angle distribution function implies the existence of the tetrahedral atomic unit in liquid Ge. The self-diffusion coefficient for the rectangular parallelepiped cell is 20{\%} larger than that of the cubic one. The obtained dynamic structure factor agrees well with the experimental one obtained by the inelastic x-ray scattering experiment, which shows the {"}de Gennes narrowing{"} of the main peak and the existence of the side peaks. These side peaks represent a longitudinal vibrational motion, which was also supported by the subsidiary peak around 30 ps-1 in the spectral density of the velocity autocorrelation function. The gradient of the dispersion relation in the present simulation agrees well with the experimental sound velocity. This {"}no positive dispersion{"} accords well with the inelastic x-ray scattering experiment of Hosokawa The reason for this {"}no positive dispersion{"} for liquid Ge is discussed in particular concern with its low kinematic viscosity. Though the velocity autocorrelation function itself does not show a cage effect, a microscopic cage effect can be found by the detailed analysis for the trace and environment of the single atomic motion. The atomic movement as a group of 3-5 atoms seems to be present in liquid Ge in addition to individual atomic motions. The covalent bond seems to be also present at least instantaneously in liquid Ge.",
author = "S. Munejiri and Tadahiko Masaki and T. Itami and F. Shimojo and K. Hoshino",
year = "2008",
month = "1",
day = "18",
doi = "10.1103/PhysRevB.77.014206",
language = "English",
volume = "77",
journal = "Physical Review B-Condensed Matter",
issn = "0163-1829",
publisher = "American Institute of Physics Publising LLC",
number = "1",

}

TY - JOUR

T1 - Static and dynamic structure and the atomic dynamics of liquid Ge from first-principles molecular-dynamics simulations

AU - Munejiri, S.

AU - Masaki, Tadahiko

AU - Itami, T.

AU - Shimojo, F.

AU - Hoshino, K.

PY - 2008/1/18

Y1 - 2008/1/18

N2 - The first-principles molecular-dynamics simulation was performed for liquid Ge at 1253 K by using two kinds of simulation cells: The cubic cell of 64 atoms and the rectangular parallelepiped one of 128 atoms. The rectangular parallelepiped cell of 128 atoms was adopted to obtain the dynamic structure factor of liquid Ge in the small wave number region. The long simulation time was adopted, i.e., 66 ps for the cubic cell and 75 ps for the rectangular parallelepiped one. The present first-principles molecular-dynamics simulation reproduces well the experimental static structure factor and radial distribution function. A broad peak around 100° in the obtained bond angle distribution function implies the existence of the tetrahedral atomic unit in liquid Ge. The self-diffusion coefficient for the rectangular parallelepiped cell is 20% larger than that of the cubic one. The obtained dynamic structure factor agrees well with the experimental one obtained by the inelastic x-ray scattering experiment, which shows the "de Gennes narrowing" of the main peak and the existence of the side peaks. These side peaks represent a longitudinal vibrational motion, which was also supported by the subsidiary peak around 30 ps-1 in the spectral density of the velocity autocorrelation function. The gradient of the dispersion relation in the present simulation agrees well with the experimental sound velocity. This "no positive dispersion" accords well with the inelastic x-ray scattering experiment of Hosokawa The reason for this "no positive dispersion" for liquid Ge is discussed in particular concern with its low kinematic viscosity. Though the velocity autocorrelation function itself does not show a cage effect, a microscopic cage effect can be found by the detailed analysis for the trace and environment of the single atomic motion. The atomic movement as a group of 3-5 atoms seems to be present in liquid Ge in addition to individual atomic motions. The covalent bond seems to be also present at least instantaneously in liquid Ge.

AB - The first-principles molecular-dynamics simulation was performed for liquid Ge at 1253 K by using two kinds of simulation cells: The cubic cell of 64 atoms and the rectangular parallelepiped one of 128 atoms. The rectangular parallelepiped cell of 128 atoms was adopted to obtain the dynamic structure factor of liquid Ge in the small wave number region. The long simulation time was adopted, i.e., 66 ps for the cubic cell and 75 ps for the rectangular parallelepiped one. The present first-principles molecular-dynamics simulation reproduces well the experimental static structure factor and radial distribution function. A broad peak around 100° in the obtained bond angle distribution function implies the existence of the tetrahedral atomic unit in liquid Ge. The self-diffusion coefficient for the rectangular parallelepiped cell is 20% larger than that of the cubic one. The obtained dynamic structure factor agrees well with the experimental one obtained by the inelastic x-ray scattering experiment, which shows the "de Gennes narrowing" of the main peak and the existence of the side peaks. These side peaks represent a longitudinal vibrational motion, which was also supported by the subsidiary peak around 30 ps-1 in the spectral density of the velocity autocorrelation function. The gradient of the dispersion relation in the present simulation agrees well with the experimental sound velocity. This "no positive dispersion" accords well with the inelastic x-ray scattering experiment of Hosokawa The reason for this "no positive dispersion" for liquid Ge is discussed in particular concern with its low kinematic viscosity. Though the velocity autocorrelation function itself does not show a cage effect, a microscopic cage effect can be found by the detailed analysis for the trace and environment of the single atomic motion. The atomic movement as a group of 3-5 atoms seems to be present in liquid Ge in addition to individual atomic motions. The covalent bond seems to be also present at least instantaneously in liquid Ge.

UR - http://www.scopus.com/inward/record.url?scp=38649121482&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=38649121482&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.77.014206

DO - 10.1103/PhysRevB.77.014206

M3 - Article

AN - SCOPUS:38649121482

VL - 77

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 0163-1829

IS - 1

M1 - 014206

ER -