Vinay Vaibhav The Institute of Mathematical Sciences Chennai, India Jürgen Horbach Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany Pinaki Chaudhuri The Institute of Mathematical Sciences Chennai, India arXiv:2202.12612 arXiv:2202.12189
dispersity are ubiquitous # Microscopic understanding of dynamics and rheology; developing applications and design materials # Structural changes with inclusion of small particles: softening and then hardening # Regime of interest: fl uid of smaller particles in the glassy matrix of bigger species # Smaller particles also form glass at higher packing fraction
species # Bigger particles show glass transition: described by mode-coupling theory # Smaller particles moving in the glassy matrix of bigger species: localization transition Binary mixture with large bidispersity
shear competes with the widely separated relaxation timescales of bigger and smaller species Our goal Detailed microscopic understanding of macroscopic observations
repulsive part # 50-50 mixture; A: large and B: small # Mean diameter ratio: # Bigger species mostly occupy the volume # Bigger particles are polydisperse: # Weaker cross-coupling: # Temperature of the system is fi xed (T = 2/3) # High density: hybrid swap MC-MD <latexit sha1_base64="KO24NaJnfxVOAyQuD8Xy62qnL6k=">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</latexit> V↵ (r) = 4✏↵ ⇥ ( ↵ r )12 ( ↵ r )6 ⇤ + ✏↵ <latexit sha1_base64="0Q2z/2yQeVtpVdd5P6EkojtxXq4=">AAACAnicdVC7SgNBFJ31GeMraiU2g1GwWmciZhUsRBtLBROFJIbZyawZMvtg5q4YlmDjr9hYKGLrV9j5N04egoqe6nDOvdxzj58oaYCQD2dsfGJyajo3k5+dm19YLCwtV02cai4qPFaxvvSZEUpGogISlLhMtGChr8SF3znu+xc3QhsZR+fQTUQjZNeRDCRnYKVmYXWjDuIWsiDWuIexPsClq4xul3sbzUKRuPseKVOCiet5tLy/a0nJoztkD1OXDFBEI5w2C+/1VszTUETAFTOmRkkCjYxpkFyJXr6eGpEw3mHXomZpxEJhGtnghR7etEoL91MEcQR4oH7fyFhoTDf07WTIoG1+e33xL6+WQrDXyGSUpCAiPjwUpApDjPt94JbUgoPqWsK4ljYr5m2mGQfbWt6W8PUp/p9USy4tu/SsVDw8GtWRQ2toHW0hijx0iE7QKaogju7QA3pCz8698+i8OK/D0TFntLOCfsB5+wQLGJXs</latexit> for r < 21/6 <latexit sha1_base64="bQwyqln0RtncybAoKiIpgm2pREw=">AAACEXicdVDLTgIxFO3gC/GFunTTCCasxs4YGNgBblxiIo8ECOmUAg2dR9qOkUz4BTf+ihsXGuPWnTv/xvJK1OhJbnJ6zr3pvccNOZMKoU8jsba+sbmV3E7t7O7tH6QPjxoyiAShdRLwQLRcLClnPq0rpjhthYJiz+W06Y4vZ37zlgrJAv9GTULa9fDQZwNGsNJSL53LdiQbergXVypTeA5Xr2p1Cjs4DEVwB22zmM/20hlklhxUsBBEpuNYhVJeE9uxLlARWiaaIwOWqPXSH51+QCKP+opwLGXbQqHqxlgoRjidpjqRpCEmYzykbU197FHZjecXTeGZVvpwEAhdvoJz9ftEjD0pJ56rOz2sRvK3NxP/8tqRGhS7MfPDSFGfLD4aRByqAM7igX0mKFF8ogkmguldIRlhgYnSIaZ0CKtL4f+kYZtWwbSu7Uy5uowjCU7AKcgBCzigDK5ADdQBAffgETyDF+PBeDJejbdFa8JYzhyDHzDevwD0rJvW</latexit> AA/ BB ⇡ 2.85 <latexit sha1_base64="jq9dqerMhiPnBxzvxU19pblHIGo=">AAACBHicdVBLTwIxGOziC/G16pFLI5h42rQYWEg8gF48YiJgAoR0S4GG7iNt14RsOHjxr3jxoDFe/RHe/DeWh4kanaTJdGa+tN94keBKI/RhpVZW19Y30puZre2d3T17/6CpwlhS1qChCOWNRxQTPGANzbVgN5FkxPcEa3nji5nfumVS8TC41pOIdX0yDPiAU6KN1LOzeeSUi/AMdhQf+qSX1GpTc8MOLuZ7dg45FReVMILIcV1cqhQNKbj4FJVNBM2RA0vUe/Z7px/S2GeBpoIo1cYo0t2ESM2pYNNMJ1YsInRMhqxtaEB8prrJfIkpPDZKHw5CaU6g4Vz9PpEQX6mJ75mkT/RI/fZm4l9eO9aDcjfhQRRrFtDFQ4NYQB3CWSOwzyWjWkwMIVRy81dIR0QSqk1vGVPC16bwf9IsOLjk4KtCrnq+rCMNsuAInAAMXFAFl6AOGoCCO/AAnsCzdW89Wi/W6yKaspYzh+AHrLdP+g2VIg==</latexit> 0.85 < AA < 1.15 <latexit sha1_base64="Jb10+VwBdJkIcA7ogtbVQxEUGi8=">AAAB/XicdVDJSgNBEO1xjXEbl5uXxkTwNPQkJJMchBAvHiOYBZJh6Ol0kiY9C909QhyCv+LFgyJe/Q9v/o2dRVDRBwWP96qoqufHnEmF0Iexsrq2vrGZ2cpu7+zu7ZsHhy0ZJYLQJol4JDo+lpSzkDYVU5x2YkFx4HPa9seXM799S4VkUXijJjF1AzwM2YARrLTkmcf5nmTDAHtpvT6FFxBZxVLeM3PIqjqobCMtOI5drpY0KTh2EVWgbaE5cmCJhme+9/oRSQIaKsKxlF0bxcpNsVCMcDrN9hJJY0zGeEi7moY4oNJN59dP4ZlW+nAQCV2hgnP1+0SKAyknga87A6xG8rc3E//yuokaVNyUhXGiaEgWiwYJhyqCsyhgnwlKFJ9ogolg+lZIRlhgonRgWR3C16fwf9IqWHbZsq8LuVp9GUcGnIBTcA5s4IAauAIN0AQE3IEH8ASejXvj0XgxXhetK8Zy5gj8gPH2Ce7ik5k=</latexit> BB = 0.35 <latexit sha1_base64="lFsZC0p4jEQ497gaiSXNGDBxSwQ=">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</latexit> ✏AB = 0.1; ✏AA = ✏BB = 1.0 LAMMPS: Molecular dynamics simulation ! Density of the system is varied ! Ref: Voigtmann and Horbach, PRL (2009)
xA = xB = 0.5 <latexit sha1_base64="daT4WAnmYeKAqs52QXH/HteoaBc=">AAACBHicbVC7TsMwFHXKq5RXgLGLRYvEVCUdgLEtHZhQkehDakPkuE5r1U4i20Gqogws/AoLAwix8hFs/A1umwFajmTp6Jx7dX2OFzEqlWV9G7m19Y3Nrfx2YWd3b//APDzqyDAWmLRxyELR85AkjAakrahipBcJgrjHSNebXM387gMRkobBnZpGxOFoFFCfYqS05JrFctNN6o0UDiIRRiqEN7Dp1u8TzNOya5asijUHXCV2RkogQ8s1vwbDEMecBAozJGXftiLlJEgoihlJC4NYkgjhCRqRvqYB4kQ6yTxECk+1MoR+KPQLFJyrvzcSxKWcck9PcqTGctmbif95/Vj5l05CgyhWJMCLQ37MoA47awQOqSBYsakmCAuq/wrxGAmEle6toEuwlyOvkk61Yp9X7NtqqdbI6siDIjgBZ8AGF6AGrkELtAEGj+AZvII348l4Md6Nj8Vozsh2jsEfGJ8/s0WW2w==</latexit> DAB / NDcm A # Interdiffusion: relaxation of concentration fl uctuation # Track centre-of-mass motion of bigger species # Center of mass MSD: # Interdiffusion coef fi cient: # For our system: Interdiffusive precocess in the context of binary mixture with large size ratio? Ref: V. Vaibhav, J. Horbach, and P. Chaudhuri; arXiv: 2202.12189
2.205 2.296 2.500 3.000 3.500 10°4 10°2 100 102 hdr2 A (t)i (b) 10°1 101 103 105 t 10°4 10°2 100 102 104 hdr2 B (t)i (c) 2.00 2.25 2.50 2.75 3.00 r 10°7 10°5 10°3 10°1 Diffusion coefficient DA DB Dcm A DAB Diffusion and interdiffusion MSD: center of mass (A) MSD: bigger species MSD: smaller species Interdiffusion Smaller species Bigger species # Bigger particles show fi nite diffusion at higher densities beyond MCT # At higher densities, bigger particle diffusion is same as COM diffusion # Interdiffusion follows the motion of smaller species Ref: V. Vaibhav, J. Horbach, and P. Chaudhuri; arXiv: 2202.12189
2.205 2.296 2.500 3.000 3.500 10°4 10°2 100 102 hdr2 A (t)i (b) 10°1 101 103 105 t 10°4 10°2 100 102 104 hdr2 B (t)i (c) 2.00 2.25 2.50 2.75 3.00 r 10°7 10°5 10°3 10°1 Diffusion coefficient ˜ DA DA DB Dcm A DAB Solid line: Usual de fi nition Dashed line: Modi fi ed de fi nition; quantity wrt respective centre of mass Dynamics with centre of mass correction Interdiffusion Smaller species Bigger species # Recti fi cation: measurement in respective centre of mass frame Ref: V. Vaibhav, J. Horbach, and P. Chaudhuri; arXiv: 2202.12189 Center of mass: bigger species MSD: bigger species MSD: smaller species
0.0 0.2 0.4 0.6 0.8 1.0 g 0.0 0.4 0.8 1.2 sXY ˙ g = 4e ° 6 ˙ g = 1e ° 5 ˙ g = 1e ° 4 ˙ g = 1e ° 3 10°4 10°2 100 102 hdr2 A (t)i 1.050 1.087 1.095 1.103 1.113 1.125 1.148 1.250 1.500 1.750 10°1 101 103 105 t 10°4 10°2 100 102 104 hdr2 B (t)i Bigger species Smaller species rho_A Stress-strain Quiescent MSD # Shear XY plane along X with different shear-rates # Nonequilibrium steady state: system yields and shear-stress becomes steady; measurements are done in y directions # Interplay of different time-scales: timescale introduced by shear competes with the relaxation timescales associated with two species Control parameter: shear-rate and density Timescale separation Ref: V. Vaibhav, J. Horbach, and P. Chaudhuri; arXiv: 2202.12612
displacement Density dependent response of the particles 10°5 10°3 10°1 101 103 hdy2 A (t)i (a) 1.0e ° 3 1.0e ° 4 1.0e ° 5 0.0 (b) (c) 10°1 101 103 105 t 10°5 10°3 10°1 101 103 hdy2 B (t)i (d) 10°1 101 103 105 t (e) 10°1 101 103 105 t (f ) Shear-rate Micro picture: MSD # Smaller densities below MCT: dynamics under shear is similar to equilibrium dynamics # Densities close to MCT: bigger species respond to shear; smaller species continues to follow equilibrium dynamics # Higher density above MCT: both species respond to shear rhoA_MCT = 1.115 Bigger species Smaller species
of smaller species into the mixture lowers the viscosity i.e., softening of the material # Similar observations in colloidal and granular systems Symbol Composition A-B circle 100-0 square 75-25 triangle 50-50 10°1 101 103 105 t 10°4 10°2 100 102 hdr2 A (t)i 1.113 1.050 1.05 1.08 1.11 rA 10°6 10°4 10°2 DA 100-0 75-25 50-50 10°2 10°1 100 sxy( ˙ g) 1.113 1.087 103 104 105 h( ˙ g) 1.113 1.087 10°6 10°5 10°4 10°3 ˙ g 10°5 10°4 10°3 DA 1.087 1.113 Diffusion coef fi cient Varying composition: role of smaller particles Ref: V. Vaibhav, J. Horbach, and P. Chaudhuri; arXiv: 2202.12612
binary mixture with large size disparity # Finite interdiffusion beyond glass formation by bigger species ==> single particle data needs centre-of mass correction # Timescale separation between species: density dependent response to the shear # Shear: connecting microscopic observations with macro response # Varying the composition of the mixture Finite-size effects in the diffusion dynamics of a glassforming binary mixture with large size ratio Vinay Vaibhav, Juergen Horbach, and Pinaki Chaudhuri; arXiv: 2202.12189 Rheological response of a glass-forming liquid having large bidispersity Vinay Vaibhav, Juergen Horbach, and Pinaki Chaudhuri; arXiv: 2202.12612 Conclusions 2.00 2.25 2.50 2.75 3.00 r 10°7 10°5 10°3 10°1 Diffusion coefficient ˜ DA DA DB Dcm A DAB 10°6 10°5 10°4 10°3 ˙ g 10°3 10°1 101 sxy( ˙ g) 10°1 101 103 105 t 10°4 10°2 100 102 hdr2 A (t)i 1.113 1.050 1.05 1.08 1.11 rA 10°6 10°4 10°2 DA 100-0 75-25 50-50
binary mixture with large size disparity # Finite interdiffusion beyond glass formation by bigger species ==> single particle data needs centre-of mass correction # Timescale separation between species: density dependent response to the shear # Shear: connecting microscopic observations with macro response # Varying the composition of the mixture Finite-size effects in the diffusion dynamics of a glassforming binary mixture with large size ratio Vinay Vaibhav, Juergen Horbach, and Pinaki Chaudhuri; arXiv: 2202.12189 Rheological response of a glass-forming liquid having large bidispersity Vinay Vaibhav, Juergen Horbach, and Pinaki Chaudhuri; arXiv: 2202.12612 Conclusions 2.00 2.25 2.50 2.75 3.00 r 10°7 10°5 10°3 10°1 Diffusion coefficient ˜ DA DA DB Dcm A DAB 10°6 10°5 10°4 10°3 ˙ g 10°3 10°1 101 sxy( ˙ g) 10°1 101 103 105 t 10°4 10°2 100 102 hdr2 A (t)i 1.113 1.050 1.05 1.08 1.11 rA 10°6 10°4 10°2 DA 100-0 75-25 50-50 ThankYou