# Yield stress discontinuity in a simple glass

F. Varnik, O. Henrich

Research output: Contribution to journalArticle

42 Citations (Scopus)

### Abstract

Large scale molecular dynamics simulations are performed to study the steady state yielding dynamics of a well established simple glass. In contrast to the supercooled state, where the shear stress, $\sigma$, tends to zero at vanishing shear rate, $\gammadot$, a stress plateau forms in the glass which extends over about two decades in shear rate. This strongly suggests the existence of a finite dynamic yield stress in the glass, $\sigma^+ (T) \equiv \sigma(T; \gammadot \to 0) >0$. Furthermore, the temperature dependence of $\sigma^+$ suggests a yield stress discontinuity at the glass transition in agreement with recent theoretical predictions. We scrutinize and support this observation by testing explicitly for the assumptions (affine flow, absence of flow induced ordering) inherent in the theory. Also, a qualitative change of the flow curves enables us to bracket the glass transition temperature $T_c$ of the theory from above and (for the first time in simulations) {\it from below}. Furthermore, the structural relaxation time in the steady state behaves quite similar to the system viscosity at all studied shear rates and temperatures.
Original language Undefined/Unknown 174209 5 Physical Review B (Condensed Matter) 73 https://doi.org/10.1103/PhysRevB.73.174209 Published - 24 May 2006

• shear rate
• shear stress
• yield stress
• flow curves

### Cite this

@article{10da82d07304495d811c7a45dfe789f1,
title = "Yield stress discontinuity in a simple glass",
abstract = "Large scale molecular dynamics simulations are performed to study the steady state yielding dynamics of a well established simple glass. In contrast to the supercooled state, where the shear stress, $\sigma$, tends to zero at vanishing shear rate, $\gammadot$, a stress plateau forms in the glass which extends over about two decades in shear rate. This strongly suggests the existence of a finite dynamic yield stress in the glass, $\sigma^+ (T) \equiv \sigma(T; \gammadot \to 0) >0$. Furthermore, the temperature dependence of $\sigma^+$ suggests a yield stress discontinuity at the glass transition in agreement with recent theoretical predictions. We scrutinize and support this observation by testing explicitly for the assumptions (affine flow, absence of flow induced ordering) inherent in the theory. Also, a qualitative change of the flow curves enables us to bracket the glass transition temperature $T_c$ of the theory from above and (for the first time in simulations) {\it from below}. Furthermore, the structural relaxation time in the steady state behaves quite similar to the system viscosity at all studied shear rates and temperatures.",
keywords = "shear rate, shear stress, yield stress, flow curves",
author = "F. Varnik and O. Henrich",
year = "2006",
month = "5",
day = "24",
doi = "10.1103/PhysRevB.73.174209",
language = "Undefined/Unknown",
volume = "73",
journal = "Physical Review B (Condensed Matter)",
issn = "0163-1829",

}

In: Physical Review B (Condensed Matter), Vol. 73, 174209, 24.05.2006.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Yield stress discontinuity in a simple glass

AU - Varnik, F.

AU - Henrich, O.

PY - 2006/5/24

Y1 - 2006/5/24

N2 - Large scale molecular dynamics simulations are performed to study the steady state yielding dynamics of a well established simple glass. In contrast to the supercooled state, where the shear stress, $\sigma$, tends to zero at vanishing shear rate, $\gammadot$, a stress plateau forms in the glass which extends over about two decades in shear rate. This strongly suggests the existence of a finite dynamic yield stress in the glass, $\sigma^+ (T) \equiv \sigma(T; \gammadot \to 0) >0$. Furthermore, the temperature dependence of $\sigma^+$ suggests a yield stress discontinuity at the glass transition in agreement with recent theoretical predictions. We scrutinize and support this observation by testing explicitly for the assumptions (affine flow, absence of flow induced ordering) inherent in the theory. Also, a qualitative change of the flow curves enables us to bracket the glass transition temperature $T_c$ of the theory from above and (for the first time in simulations) {\it from below}. Furthermore, the structural relaxation time in the steady state behaves quite similar to the system viscosity at all studied shear rates and temperatures.

AB - Large scale molecular dynamics simulations are performed to study the steady state yielding dynamics of a well established simple glass. In contrast to the supercooled state, where the shear stress, $\sigma$, tends to zero at vanishing shear rate, $\gammadot$, a stress plateau forms in the glass which extends over about two decades in shear rate. This strongly suggests the existence of a finite dynamic yield stress in the glass, $\sigma^+ (T) \equiv \sigma(T; \gammadot \to 0) >0$. Furthermore, the temperature dependence of $\sigma^+$ suggests a yield stress discontinuity at the glass transition in agreement with recent theoretical predictions. We scrutinize and support this observation by testing explicitly for the assumptions (affine flow, absence of flow induced ordering) inherent in the theory. Also, a qualitative change of the flow curves enables us to bracket the glass transition temperature $T_c$ of the theory from above and (for the first time in simulations) {\it from below}. Furthermore, the structural relaxation time in the steady state behaves quite similar to the system viscosity at all studied shear rates and temperatures.

KW - shear rate

KW - shear stress

KW - yield stress

KW - flow curves

UR - https://journals.aps.org/prb/

U2 - 10.1103/PhysRevB.73.174209

DO - 10.1103/PhysRevB.73.174209

M3 - Article

VL - 73

JO - Physical Review B (Condensed Matter)

JF - Physical Review B (Condensed Matter)

SN - 0163-1829

M1 - 174209

ER -