# Entropy, diffusivity and the energy landscape of a water-like fluid 

Departamento de F´ısica, Universidade Federal de Ouro Preto, 

Instituto de F´ısica, Universidade Federal do Rio Grande do Sul, 

Ouro Preto, MG, 35400-000, Brazil ∗ 

Porto Alegre, RS, 91501-970, BRAZIL † 

Alan Barros de Oliveira 

Charusita Chakravarty 

Evy Salcedo 

Department of Chemistry, Indian Institute of Technology-Delhi, New Delhi, 110016, India ‡ 

Instituto de F´ısica,Universidade Federal do Rio Grande do Sul, 

Porto Alegre, RS, 91501-970, Brazil § 

Marcia C. Barbosa 

## Abstract 

Molecular dynamics simulations and instantaneous normal mode (INM) analysis of a fluid with core-softened pair interactions and water-like liquid-state anomalies are performed to obtain an understanding of the relationship between thermodynamics, transport properties and the poten- tial energy landscape. Rosenfeld-scaling of diffusivities with the thermodynamic excess and pair correlation entropy is demonstrated for this model. The INM spectra are shown to carry infor- mation about the dynamical consequences of the interplay between length scales characteristic of anomalous fluids, such as bimodality of the real and imaginary branches of the frequency distribu- tion. The INM spectral information is used to partition the liquid entropy into two contributions associated with the real and imaginary frequency modes; only the entropy contribution from the imaginary branch captures the non-monotonic behaviour of the excess entropy and diffusivity in the anomalous regime of the fluid. 

PACS numbers: 64.70.Pf, 82.70.Dd, 83.10.Rs, 61.20.Ja 

