Breakdown of the Stokes-Einstein relation in Stillinger-Weber Silicon
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| Format: | Preprint |
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2025
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| _version_ | 1866909550118961152 |
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| author | Rautela, Himani Sengupta, Shiladitya Vasisht, Vishwas V. |
| author_facet | Rautela, Himani Sengupta, Shiladitya Vasisht, Vishwas V. |
| contents | We investigate the dynamical properties of liquid and supercooled liquid silicon, modeled using the Stillinger-Weber (SW) potential, to examine the validity of the Stokes-Einstein (SE) relation. Towards this end, we examine the relationship among various dynamical quantities, including (i) the macroscopic transport coefficients - self diffusion coefficient $D$ and viscosity $η$, (ii) relaxation time $τ_α$ as well as (iii) lengthscale dependent relaxation times $τ_α(q)$ over a broad range of temperature $T$, pressure $P$ and density $ρ$ covering both equilibrium and metastable liquid state points in the phase diagram. Our study shows a weak break down in SE relation involving $D$ and $η$, and the loci of \Revision{the breakdown of the SE relation} (SEB) is found in the high T liquid phase. The $τ_α$, when used as a proxy to $η$, shows distinct breakdown in the SE relation whose loci is found in the supercooled liquid phase. Interestingly, certain parts of the phase diagram shows that loci of onset of slow dynamics lie below the loci of SEB, suggesting a regime that exhibits Arrhenius but non-Fickian behaviour. Computation of $τ_α(q)$ enables us to extract the lengthscale associated with the Fickian to non-Fickian behaviour using which we show that the \Revision{breakdown of the SE relation} occurs only below a specific lengthscale at a given temperature. Further we also compare the SEB loci with other features of the phase behaviour, including the loci of compressiblity maximum, density maximum as well as diffusivity maximum. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_18498 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Breakdown of the Stokes-Einstein relation in Stillinger-Weber Silicon Rautela, Himani Sengupta, Shiladitya Vasisht, Vishwas V. Materials Science Soft Condensed Matter Statistical Mechanics We investigate the dynamical properties of liquid and supercooled liquid silicon, modeled using the Stillinger-Weber (SW) potential, to examine the validity of the Stokes-Einstein (SE) relation. Towards this end, we examine the relationship among various dynamical quantities, including (i) the macroscopic transport coefficients - self diffusion coefficient $D$ and viscosity $η$, (ii) relaxation time $τ_α$ as well as (iii) lengthscale dependent relaxation times $τ_α(q)$ over a broad range of temperature $T$, pressure $P$ and density $ρ$ covering both equilibrium and metastable liquid state points in the phase diagram. Our study shows a weak break down in SE relation involving $D$ and $η$, and the loci of \Revision{the breakdown of the SE relation} (SEB) is found in the high T liquid phase. The $τ_α$, when used as a proxy to $η$, shows distinct breakdown in the SE relation whose loci is found in the supercooled liquid phase. Interestingly, certain parts of the phase diagram shows that loci of onset of slow dynamics lie below the loci of SEB, suggesting a regime that exhibits Arrhenius but non-Fickian behaviour. Computation of $τ_α(q)$ enables us to extract the lengthscale associated with the Fickian to non-Fickian behaviour using which we show that the \Revision{breakdown of the SE relation} occurs only below a specific lengthscale at a given temperature. Further we also compare the SEB loci with other features of the phase behaviour, including the loci of compressiblity maximum, density maximum as well as diffusivity maximum. |
| title | Breakdown of the Stokes-Einstein relation in Stillinger-Weber Silicon |
| topic | Materials Science Soft Condensed Matter Statistical Mechanics |
| url | https://arxiv.org/abs/2503.18498 |