# Molecular dynamics study of the mechanical loss in amorphous pure and doped silica

## Abstract

Gravitational wave detectors and other precision measurement devices are limited by the thermal noise in the oxide coatings on the mirrors of such devices. We have investigated the mechanical loss in amorphous oxides by calculating the internal friction using classical, atomistic molecular dynamics simulations. We have implemented the trajectory bisection method and the non-local ridge method in the DL-POLY molecular dynamics simulation software to carry out those calculations. These methods have been used to locate the local potential energy minima that a system visits during a molecular dynamics trajectory and the transition state between any two consecutive minima. Using the numerically calculated barrier height distributions, barrier asymmetry distributions, relaxation times, and deformation potentials, we have calculated the internal friction of pure amorphous silica and silica mixed with other oxides. The results for silica compare well with experiment. Finally, we use the numerical calculations to comment on the validity of previously used theoretical assumptions.

- Authors:

- Department of Physics and Quantum Theory Project, University of Florida, Gainesville, Florida 32611 (United States)

- Publication Date:

- OSTI Identifier:
- 22419997

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 5; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACCURACY; DOPED MATERIALS; GRAVITATIONAL WAVE DETECTORS; MOLECULAR DYNAMICS METHOD; OXIDES; POTENTIAL ENERGY; SILICA; SIMULATION

### Citation Formats

```
Hamdan, Rashid, Trinastic, Jonathan P., and Cheng, H. P., E-mail: cheng@qtp.ufl.edu.
```*Molecular dynamics study of the mechanical loss in amorphous pure and doped silica*. United States: N. p., 2014.
Web. doi:10.1063/1.4890958.

```
Hamdan, Rashid, Trinastic, Jonathan P., & Cheng, H. P., E-mail: cheng@qtp.ufl.edu.
```*Molecular dynamics study of the mechanical loss in amorphous pure and doped silica*. United States. doi:10.1063/1.4890958.

```
Hamdan, Rashid, Trinastic, Jonathan P., and Cheng, H. P., E-mail: cheng@qtp.ufl.edu. Thu .
"Molecular dynamics study of the mechanical loss in amorphous pure and doped silica". United States.
doi:10.1063/1.4890958.
```

```
@article{osti_22419997,
```

title = {Molecular dynamics study of the mechanical loss in amorphous pure and doped silica},

author = {Hamdan, Rashid and Trinastic, Jonathan P. and Cheng, H. P., E-mail: cheng@qtp.ufl.edu},

abstractNote = {Gravitational wave detectors and other precision measurement devices are limited by the thermal noise in the oxide coatings on the mirrors of such devices. We have investigated the mechanical loss in amorphous oxides by calculating the internal friction using classical, atomistic molecular dynamics simulations. We have implemented the trajectory bisection method and the non-local ridge method in the DL-POLY molecular dynamics simulation software to carry out those calculations. These methods have been used to locate the local potential energy minima that a system visits during a molecular dynamics trajectory and the transition state between any two consecutive minima. Using the numerically calculated barrier height distributions, barrier asymmetry distributions, relaxation times, and deformation potentials, we have calculated the internal friction of pure amorphous silica and silica mixed with other oxides. The results for silica compare well with experiment. Finally, we use the numerical calculations to comment on the validity of previously used theoretical assumptions.},

doi = {10.1063/1.4890958},

journal = {Journal of Chemical Physics},

number = 5,

volume = 141,

place = {United States},

year = {Thu Aug 07 00:00:00 EDT 2014},

month = {Thu Aug 07 00:00:00 EDT 2014}

}