Equilibrium States Corresponding to Targeted Hyperuniform Nonequilibrium Pair Statistics Haina Wang1and Salvatore Torquato2 3a

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Equilibrium States Corresponding to Targeted Hyperuniform Nonequilibrium Pair
Statistics
Haina Wang1and Salvatore Torquato2, 3, a)
1)Department of Chemistry, Princeton University, Princeton, New Jersey, 08544,
USA
2)Department of Chemistry, Department of Physics, Princeton Institute of Materials,
and Program in Applied and Computational Mathematics, Princeton University,
Princeton, New Jersey 08544, USA
3)School of Natural Sciences, Institute for Advanced Study, 1 Einstein Drive,
Princeton, NJ 08540, USA
1
arXiv:2210.06446v3 [cond-mat.soft] 19 Dec 2022
The Zhang-Torquato conjecture [Phys. Rev. E 101, 032124 (2020)] states that any
realizable pair correlation function g2(r) or structure factor S(k) of a translation-
ally invariant nonequilibrium system can be attained by an equilibrium ensemble
involving only (up to) effective two-body interactions. To further test and study this
conjecture, we consider two singular nonequilibrium models of recent interest that
also have the exotic hyperuniformity property: a 2D “perfect glass” and a 3D criti-
cal absorbing-state model. We find that each nonequilibrium target can be achieved
accurately by equilibrium states with effective one- and two-body potentials, lending
further support to the conjecture. To characterize the structural degeneracy of such
a nonequilibrium-equilibrium correspondence, we compute higher-order statistics for
both models, as well as those for a hyperuniform 3D uniformly randomized lattice
(URL), whose higher-order statistics can be very precisely ascertained. Interestingly,
we find that the differences in the higher-order statistics between nonequilibrium
and equilibrium systems with matching pair statistics, as measured by the “hole”
probability distribution, provides measures of the degree to which a system is out
of equilibrium. We show that all three systems studied possess the bounded-hole
property, and that holes near the maximum hole size in the URL are much rarer
than those in the underlying simple cubic lattice. Remarkably, upon quenching,
the effective potentials for all three systems possess local energy minima (i.e., in-
herent structures) with stronger forms of hyperuniformity compared to their target
counterparts. Our methods are expected to facilitate the self-assembly of tunable
hyperuniform soft-matter systems.
a)Email: torquato@princeton.edu
2
I. INTRODUCTION
Probing and characterizing structural properties of many-body systems in and out of
equilibrium is a crucial task in the understanding of a large variety of physical, chemical
and biological phenomena.15An outstanding challenge is the determination of effective
interactions in many-body systems that accurately yield equilibrium states with prescribed
pair statistics. Solving such inverse problems is a powerful way to tackle the unsolved
problem concerning the realizability of prescribed functional forms of pair statistics by many-
body systems.611 Such investigations also enable one to probe systems with identical pair
statistics but different higher-body statistics, which is expected to shed light on the well-
known degeneracy problem of statistical mechanics.1214 Moreover, such effective potentials
can be used to model macromolecules and solutions,15,16 and to design nanoparticles that
self-assemble into desired structures, thereby facilitating material discovery.1720
Recently, Zhang and Torquato conjectured that any realizable pair correlation function
g2(r) or structure factor S(k) corresponding to a translationally invariant nonequilibrium
system can be attained by an equilibrium ensemble involving only one- and two-body ef-
fective interactions at positive temperatures.11 Testing the conjecture requires the precise
determination of the effective interactions for a spectrum of target systems, including those
with the exotic hyperuniform property.21,22 Disordered hyperuniform many-body systems,
which can be solid and fluid states, are unusual amorphous states of matter that lie be-
tween a crystal and liquid. They are like perfect crystals in the way they suppress large-
scale density fluctuations, and yet are like liquids or glasses in that they are statistically
isotropic with no Bragg peaks;21,22 see Sec. II B for precise definitions. Disordered hype-
runiform states play vital roles in a variety of different contexts. For example, disordered
stealthy ground states have been discovered2325 corresponding to under soft, long-ranged
interactions, which are highly degenerate and have the “bounded-hole” property, which is
a singular characteristic for a disordered system.26,27 Network structures derived from dis-
ordered stealthy point patterns can achieve complete photonic band gaps and have novel
optical properties that were previously not thought to be possible.28,29 Disordered hype-
runiform states also arise in the eigenvalues of random matrices (such as the Gaussian
unitary ensemble),3032 ground states of free fermions,31 as well as one-component plas-
mas at positive temperatures,3335 all of which are exotic fluid states in which the par-
3
ticles interact Coulombically.36 Other examples include including glass formation,22,37,38
jamming,3943 rigidity,38,44 biology,45,46 localization of waves and excitations,4750 antenna
or laser array designs,51 self-organization,5254 fluid dynamics,5557 quantum systems,31,5861
and pure mathematics.6266 Because disordered hyperuniform states combine the advantages
of statistical isotropy and the suppression of density fluctuations on large scales, they can
be endowed with novel physical properties.22,28,29,37,38,45,46,5254,67
While Zhang and Torquato introduced an algorithm to draw equilibrium classical parti-
cle configurations from canonical ensembles with one- and two-body interactions that cor-
respond to targeted functional forms for g2(r) or S(k), the algorithm does not generate
explicit forms of the potentials.11 Very recently, Torquato and Wang developed an inverse
methodology that determines effective interactions with unprecedented accuracy.68 Using
this procedure, they demonstrated the realizability of g2(r) for all rand S(k) for all kfor
two different nonequilibrium models, including a two-dimensional (2D) nonhyperuniform
random sequential addition process and a 3D hyperuniform “cloaked” uniformly random-
ized lattice (URL).68 However, the Zhang-Torquato conjecture remains largely untested.
In this paper, we utilize this precise inverse methodology68 to further test and study the
Zhang-Torquato conjecture for unusual nonequilibrium hyperuniform systems. Hyperuni-
form targets are particularly challenging because at positive temperature Tthey require a
long-ranged pair interaction v(r) that must be balanced by one-body potentials to stabilize
the equilibrium system.22
Prior to the development of our inverse methodology,68 predictor-corrector methods,6972
such as Iterative Boltzmann inversion (IBI)71 and iterative hypernetted chain inversion
(IHNCI),72,73 were regarded to be the most accurate inverse procedures. Both IBI and
IHNCI begin with an initial discretized (binned) approximation of a trial pair potential.
The trial pair potential at each binned distance is iteratively updated to attempt to reduce
the difference between the target and trial pair statistics. However, IBI and IHNCI cannot
treat long-ranged pair interactions required for hyperuniform targets, nor do they consider
one-body interactions that stabilize hyperuniform equilibrium states;68 see Sec. II B for
details. These algorithms also accumulate random errors in the binned potentials due to
simulation errors in the trial pair statistics, and thus do not achieve the precision required
to probe realizability problems. Moreover, because all previous methods do not optimize a
pair-statistic “distance” functional, they are unable to detect poor agreement between the
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target and trial pair statistics that may arise as the simulation evolves, leading to increas-
ingly inaccurate corresponding trial potentials, as demonstrated in Ref. 68.
The inverse methodology presented in Ref. 68 improves on previous procedures in several
significant ways. It utilizes a parameterized family of pointwise basis functions for the
potential function at T > 0, whose initial form is informed by small- and large-distance
behaviors dictated by statistical-mechanical theory. Pointwise potential functions do not
suffer from the accumulation of random errors during a simulation, resulting in more accurate
interactions.68 Since it has recently been established74 that inverse methods that target
only g2(r) or only S(k) for a limited range of ror kmay generate effective potentials
that are distinctly different from the unique potential dictated by Henderson’s theorem,75
our methodology68 minimizes an objective function that incorporates both the target pair
correlation function g2(r) and structure factor S(k) so that both the small- and large-distance
correlations are very accurately captured. For hyperuniform targets, our methodology is able
to optimize the required long-ranged pair potential76 as well as the neutralizing background
one-body potential;68 see Sec. IV for details.
To assess the accuracy of inverse methodologies to target pair statistics, we introduced68
the following dimensionless L2-norm error:
E=pDg2+DS,(1)
where Dg2and DSare L2functions, given by
Dg2=ρZRd
[g2,T (r)g2,F (r;a)]2dr,(2)
DS=1
ρ(2π)dZRd
[ST(k)SF(k;a)]2dk,(3)
where g2,F (r;a) and SF(k;a) represent the final pair statistics at the end of the optimization,
which depend on the vector of potential parameters a. We have previously shown that our
method is able to treat challenging near-critical and hyperuniform targets,68 which previous
methods cannot do. Thus, it is the only available method to determine effective interactions
for nonequilibrium hyperuniform pair statistics. Moreover, in cases where IBI and IHNCI
are able to achieve optimized potentials, e.g., for equilibrium target pair statistics without
long-range interactions, our inverse methodology generally yields L2-norm errors (1) that are
an order of magnitude smaller than those via previous methods, and reaches the precision
required to recover the unique potential dictated by Henderson’s theorem.75
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摘要:

EquilibriumStatesCorrespondingtoTargetedHyperuniformNonequilibriumPairStatisticsHainaWang1andSalvatoreTorquato2,3,a)1)DepartmentofChemistry,PrincetonUniversity,Princeton,NewJersey,08544,USA2)DepartmentofChemistry,DepartmentofPhysics,PrincetonInstituteofMaterials,andPrograminAppliedandComputationalMa...

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