Materials in metastable states, such as amorphous ice and supercooled condensed matter, often exhibit exotic phenomena. To date, achieving metastability is usually accomplished by rapid quenching ...through a thermodynamic path function, namely, heating−cooling cycles. However, heat can be detrimental to organic-containing materials because it can induce degradation. Alternatively, the application of pressure can be used to achieve metastable states that are inaccessible via heating−cooling cycles. Here we report metastable states of 2D organic−inorganic hybrid perovskites reached through structural amorphization under compression followed by recrystallization via decompression. Remarkably, such pressure-derived metastable states in 2D hybrid perovskites exhibit enduring bandgap narrowing by as much as 8.2% with stability under ambient conditions. The achieved metastable states in 2D hybrid perovskites via compression−decompression cycles offer an alternative pathway toward manipulating the properties of these “soft” materials.
A production-level implementation of equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) for electron attachment and excitation energies augmented by a complex absorbing potential (CAP) ...is presented. The new method enables the treatment of metastable states within the EOM-CC formalism in a similar manner as bound states. The numeric performance of the method and the sensitivity of resonance positions and lifetimes to the CAP parameters and the choice of one-electron basis set are investigated. A protocol for studying molecular shape resonances based on the use of standard basis sets and a universal criterion for choosing the CAP parameters are presented. Our results for a variety of π(*) shape resonances of small to medium-size molecules demonstrate that CAP-augmented EOM-CCSD is competitive relative to other theoretical approaches for the treatment of resonances and is often able to reproduce experimental results.
Exact milestoning Bello-Rivas, Juan M; Elber, Ron
The Journal of chemical physics,
03/2015, Letnik:
142, Številka:
9
Journal Article
Recenzirano
Odprti dostop
A new theory and an exact computer algorithm for calculating kinetics and thermodynamic properties of a particle system are described. The algorithm avoids trapping in metastable states, which are ...typical challenges for Molecular Dynamics (MD) simulations on rough energy landscapes. It is based on the division of the full space into Voronoi cells. Prior knowledge or coarse sampling of space points provides the centers of the Voronoi cells. Short time trajectories are computed between the boundaries of the cells that we call milestones and are used to determine fluxes at the milestones. The flux function, an essential component of the new theory, provides a complete description of the statistical mechanics of the system at the resolution of the milestones. We illustrate the accuracy and efficiency of the exact Milestoning approach by comparing numerical results obtained on a model system using exact Milestoning with the results of long trajectories and with a solution of the corresponding Fokker-Planck equation. The theory uses an equation that resembles the approximate Milestoning method that was introduced in 2004 A. K. Faradjian and R. Elber, J. Chem. Phys. 120(23), 10880-10889 (2004). However, the current formulation is exact and is still significantly more efficient than straightforward MD simulations on the system studied.
Updated analyses of several singlet Rydberg states of O
2
via spectra involving excitation from the metastable a
1
Δ
g
and
states are presented. The high-quality FT-VUV spectra available from the ...DESIRS beamline at the SOLEIL synchrotron gives significantly improved spectra compared to previous work. The Rydberg states analysed include
v = 0-4, 3pσ
1
Π
u
v = 0-2, 3pπ
1
Δ
u
v = 0-2,
v = 0-1, 4pσ
1
Π
u
v = 0 and 4pπ
1
Δ
u
v = 0. This is complemented by high-quality ab initio calculations on the
and
1
Δ
u
Rydberg states to determine the transition moments providing the first quantitative cross-sections for Rydberg -
transitions. These are validated against the experimental data. The results suggest the most promising candidate for determining
number density is likely to be the 1-0 band of the
transition at 131.3 nm.
•The study of new unknown details in nitrogen spectroscopy is an important part of chemistry background.•A new spin-forbidden quintet-triplet C’’5Πu → B3Πg transition is predicted.•Transition ...probabilities for an unknown C’’5Пu → B3Пg system of vibronic bands are calculated.•We provide SOC constants calculated by MRCI calculations which are in a good agreement with experiment.•The experimental set-up designed to detect the C’’ → b transition can also be used to observe the A′→ a emission.
A new spin-forbidden quintet-triplet C′′5Πu → B3Πg transition is predicted in the N2 molecule on the ground of MRCI calculations with account of spin-obit coupling (SOC) by perturbation theory. The mechanism of its probability borrowing is quite similar to the recently calculated spin-forbidden electric dipole A′5Σg+ → A3Σu+ transition in the emission spectrum of the N2 molecule. Neither of the two predicted emission systems have yet been observed in electric discharges but the calculated intensity provides a good chance for their detection. Both transitions, C′′–B and A′–A, borrow intensity from the First Positive System (B3Πg → A3Σu+) and from the Herman Infrared Band (C′′5Πu → A′5Σg+). The latter spin-allowed quintet-quintet transition provides strong depletion of the upper C′′ state; nevertheless, the energy pooling collisions of the triplet N2 molecule and atomic recombination produce a permanent pumping of the C′′5Πu states leaving a prominent emission with a detectable quantum yield. The proposed C′′ → B vibronic transitions have Einstein A coefficients in the order of 105–104s −1, showing a considerable number of strong vibronic bands. As a consequence, the radiative lifetimes of the highest spin sublevel of the C′′5Πu,1 irregular state are about 10−6 s.
A new spin-forbidden quintet-triplet C′′ 5 Π u → B 3 Π g transition is predicted in the N 2 molecule on the ground of MRCI calculations with account of spin-obit coupling (SOC) by perturbation ...theory. The mechanism of its probability borrowing is quite similar to the recently calculated spin-forbidden electric dipole A′ 5 Σ g + → A 3 Σ u + transition in the emission spectrum of the N 2 molecule. Neither of the two predicted emission systems have yet been observed in electric discharges but the calculated intensity provides a good chance for their detection. Both transitions, C′′–B and A′–A, borrow intensity from the First Positive System (B 3 Π g → A 3 Σ u + ) and from the Herman Infrared Band (C′′ 5 Π u → A′ 5 Σ g + ). The latter spin-allowed quintet-quintet transition provides strong depletion of the upper C′′ state; nevertheless, the energy pooling collisions of the triplet N 2 molecule and atomic recombination produce a permanent pumping of the C′′ 5 Π u states leaving a prominent emission with a detectable quantum yield. The proposed C′′ → B vibronic transitions have Einstein A coefficients in the order of 10 5 –10 4 s − 1 , showing a considerable number of strong vibronic bands. As a consequence, the radiative lifetimes of the highest spin sublevel of the C′′ 5 Π u,1 irregular state are about 10 −6 s.
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•Revealing the independent correlation of photochromism and PersL in the same material.•Achieving the largest coloration contrast and multicolor photochromism in ...inorganics.•Demonstrating application of the light-responsive materials in flexible electronics.
Photochromism and persistent luminescence (PersL) are two fascinating light-responsive effects in phosphors, both of which have found widespread applications in optical switching, optical anticounterfeiting and information storage. However, the relationship between photochromism and PersL has not been clarified, thus greatly limiting the use and design of the light-responsive materials in multifunctional applications. Herein, taking BaMgSiO4:Eu2+, TM (TM = transition metal: Fe, Co and Cr) as model materials, we first reveal that photochromism and PersL could be two independent photophysical effects, although they are both related to the charge carrier trapping/detrapping processes. Notably, photochromism and PersL show have different responses to light wavelengths, and the depth of traps involved in the two effects is also quite different. Moreover, by codoping different transition metal elements, we obtain the largest reflectance difference of ∼71 % among inorganic photochromic materials reported thus far, and demonstrate interesting multicolor photochromism, including magenta, golden and pink. Based on their distinct response to light and temperature, a multi-functionalized optical anticounterfeiting technology is proposed, which may open up a new avenue for applying the light-responsive materials in flexible electronics and wearable devices.
Schmitt-Triggers (S/Ts) are often utilized to clean noisy analog signals at intermediate voltage values in digital circuits. However, they are vulnerable to metastability, which may cause the same ...undesired non-digital output behavior that was supposed to be removed in the first place. To enable an efficient characterization of static and dynamic metastability properties of S/Ts (e.g., the metastable voltages, the resolution time constants and the overall total resolution times), this work introduces multiple simulation approaches based on control theory, AC, DC and transient analyses. The accuracy and runtime of all methods are compared and discussed by applying them to an analytically describable idealized circuit model as well as three common circuit implementations. Altogether, this work represents a comprehensive resource for investigating the metastable behavior in S/Ts. Even more, the proposed methods are applicable beyond the S/T, enabling an efficient characterization of static and dynamic metastable behavior in general circuits as well.
We study the statistical underpinnings of life, in particular its increase in order and complexity over evolutionary time. We question some common assumptions about the thermodynamics of life. We ...recall that contrary to widespread belief, even in a closed system entropy growth can accompany an increase in macroscopic order. We view metabolism in living things as microscopic variables directly driven by the second law of thermodynamics, while viewing the macroscopic variables of structure, complexity and homeostasis as mechanisms that are entropically favored because they open channels for entropy to grow via metabolism. This perspective reverses the conventional relation between structure and metabolism, by emphasizing the role of structure for metabolism rather than the converse. Structure extends in time, preserving information along generations, particularly in the genetic code, but also in human culture. We argue that increasing complexity is an inevitable tendency for systems with these dynamics and explain this with the notion of metastable states, which are enclosed regions of the phase-space that we call “bubbles,” and channels between these, which are discovered by random motion of the system. We consider that more complex systems inhabit larger bubbles (have more available states), and also that larger bubbles are more easily entered and less easily exited than small bubbles. The result is that the system entropically wanders into ever-larger bubbles in the foamy phase space, becoming more complex over time. This formulation makes intuitive why the increase in order/complexity over time is often stepwise and sometimes collapses catastrophically, as in biological extinction.
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