187 research outputs found
First-order semidefinite programming for the two-electron treatment of many-electron atoms and molecules
No full text
The ground-state energy and properties of any many-electron atom or
molecule may be rigorously computed by variationally computing the
two-electron reduced density matrix rather than the many-electron
wavefunction. While early attempts fifty years ago to compute the
ground-state 2-RDM directly were stymied because the 2-RDM must be
constrained to represent an N-electron wavefunction, recent
advances in theory and optimization have made direct computation of
the 2-RDM possible. The constraints in the variational calculation
of the 2-RDM require a special optimization known as a semidefinite
programming. Development of first-order semidefinite programming
for the 2-RDM method has reduced the computational costs of the
calculation by orders of magnitude [Mazziotti, Phys. Rev. Lett. 93 (2004) 213001]. The variational 2-RDM approach is effective at
capturing multi-reference correlation effects that are especially
important at non-equilibrium molecular geometries. Recent work on
2-RDM methods will be reviewed and illustrated with particular
emphasis on the importance of advances in large-scale semidefinite
programming.
Iphinoe daphne Mazziotti & Lezzi 2020, n. sp.
No full text<i>Iphinoe daphne</i> n. sp. <p>Figures 2–5</p> <p> <b>Type material</b>. Holotype (MZB21008) adult male, type locality Cesenatico (st. 21), Lat. 44.128090, Lon. 12.244960, depth 3 m., 3 km offshore, soft bottom, biocenosis SFBC, data collection May 2017; paratype (MZB 21009) adult female st. 18; paratype (MZB 21010) adult male st. 22; paratype (MZB 21011) adult male st. 19; paratype (MZB 21012) adult male st. 20; paratype (MZB 21013) preadult male st. 22; paratype (MZB 21014) preadult female st. 22; paratype (MZB 21015) ovigerous female st. 21; paratype (MZB 21016) ovigerous female st. 18; paratype (MZB 21017) ovigerous female st. 19; paratype (MZB 21018) ovigerous female st. 20; paratype (ZSMA20190394) adult male st. 23; paratype (ZSMA20190395) preadult male st. 22; paratype (ZSMA20190396) adult male st. 20; paratype (ZSMA20190397) adult male st. 19; paratype (ZSMA20190398) adult male st. 18; paratype (ZSMA20190399) ovigerous female st. 22; paratype (ZSMA20190400) preadult female st. 22; paratype (ZSMA20190401) ovigerous female st. 20; paratype (ZSMA20190402) ovigerous female st. 19; paratype (ZSMA20190403) ovigerous female st. 18; paratype (CRU2019-1) adult male st. 24; paratype (CRU2019- 2) preadult male st. 24; paratype (CRU2019-3) preadult male st. 24; paratype (CRU2019-4) preadult male st. 24; paratype (CRU2019-5) preadult male st. 22; paratype (CRU2019-6) ovigerous male st. 22; paratype (CRU2019-7) ovigerous male st. 22; paratype (CRU2019-8) ovigerous male st. 24; paratype (CRU2019-9) ovigerous male st. 24; paratype (CRU2019- 10) ovigerous male st. 24.</p> <p> <b>Other material examined</b>. 4 adult males, 2 preparatory males, 20 ovigerous females, 11 subadult females, st. 15; 4 adult males, 6 ovigerous females, 4 subadult females, st. 16; 2 adult males, 2 ovigerous females, st. 18; 13 adult males, 9 preparatory males, 46 ovigerous females, 54 subadult females, st.19; 24 adult males, 12 preparatory males, 116 ovigerous females, 76 subadult females, st. 20; 6 adult males, 5 ovigerous females, 11 subadult females, st. 21; 30 adult males, 16 preparatory males, 158 ovigerous females, 65 subadult females, st. 22; 21 adult males, 26 preparatory males, 34 ovigerous females, 130 subadult females, st. 23; 12 adult males, 4 preparatory males, 44 ovigerous females, 22 subadult females, st. 24.</p> <p> <b>Etymology.</b> The epithet daphne is a noun in apposition. The species is named after the vessel used during the sampling; Daphne is also the name of the first author’s Institute Department.</p> <p> <b>Diagnosis.</b> Pointed pseudorostrum. Carapace is about twice as long as it is deep and a fifth of the total body length. Ratio CL/CD 2.2. Presence of two perianal setae and one aesthetasc on main flagellum of antenna 1. Adult male with serrated middorsal line and a sternal process tubercle of distinctly bifid apex.</p> <p> <b>Description of the holotype adult male</b> (MZB21008).</p> <p>Total length: 4.8 mm.</p> <p>Carapace about twice as long as it is deep and a fifth of the total body length (Figure 2A). The ratio CL/CD is 2.2 (Table 4). Dorsal carina armed with 6 teeth: the first immediately after the eyelobe, then following a space, the other five close to each other. Pointed pseudorostrum. Eyelobe well developed, elevated in lateral view, with 3 lenses. Branchial siphon of medium length. Frontal lobe does not extend anteriorly, the length is a third of the carapace. Anterolateral angle rounded with a few small serrations below (Figure 2B). Five free thoracic somites; the first is visible dorsally and laterally. Abdomen longer than rest of body, abdominal somites have well developed sideplates and five pairs of pleopods. Integument over the whole body exhibits a distinct reticulation, polygonal shaped under the microscope (Figure 2C). Sternite of the second thoracic segment bears a tubercle with a distinctly bifid apex (Figure 4).</p> <p>Antenna 1 article 1 shorter than the other two articles. Article 2 inclined on the basal article at an angle of 45°. Third article a little less than three quarters as long as the second. Main flagellum two short articles, distal article with one aesthetasc and one terminal seta. Vestigial accessory flagellum minute, with 2 articles and 3 small setae; distal article the shortest (Figure 2D).</p> <p>Antenna 2 longer than body length (Figure 2A, 3D). The peduncle has 4 articles; articles 1 to 4 are unarmed; article 5 has rows of sensory setae along anterior margin; flagellum articles bear a single row of setae.</p> <p>Labium has 6 apical stout distally bent flattened setae, numerous setules on both apical margin (Figure 3L).</p> <p> Mandible <i>pars incisiva</i> has 3 teeth, the lacinia mobilis has 3 teeth, there are 11 setae between lacinia mobilis and pars molaris (Figure 3H).</p> <p>Maxilla 1 inner endite has 9 stout, spiniform setae (some subdistally dentate setae) and 2 simple setae on medial and distal margin; the outer endite has 6 robust setae and 1 filament. (Figure 3I).</p> <p>Maxilla 2 endites exceed the upper margin of protopod, inner endite has 9 microserrate setae; outer endite has 14 slender curved microserrate setae and 2 simple setae on distal margin, the protopod has apical robust setae and fine setae on distal and medial inner margin (Figure 3A).</p> <p>Maxilliped 1 basis has a long endite with four apical, three simple setae and three stout setae, carpus has eight stout palmate setae on the medial margin, large propodus about 0.8 times the length of the carpus, two simple short setae and two long setae on the apical margin, a short dactylus with terminal two stout short setae (Figure 3C).</p> <p>Maxilliped 2 basis has 1 pappose seta on medial margin; merus has 1 pappose medial seta; carpus is 1 and a half times the length of the merus, with 3 pappose setae on distal medial margin; propodus is as long as the carpus, there are 4 simple setae on the medial margin and 3 pappose setae on the distal lateral margin; dactylus is a third of the length of propodus with 6 terminal setae (Figure 3B).</p> <p>Maxilliped 3 basis about 0.6 times as long as the entire maxilliped, the outer process almost reaches the merus, with two long plumose setae. There are other smaller setae on medial margin. There are several plumose setae on the merus distal margin. Ischium and merus are as long as the carpus and propodus put together (Figure 2E).</p> <p>Pereopod 1 basis weakly arcuate, moderately longer than the rest of the limb, dully serrate on the outer edge. Merus twice as long as the ischium, carpus and propodus are the same length. Dactylus shorter than the propodus, ending with 5 long terminal simple setae (Figure 2F).</p> <p>Pereopod 2 basis slightly shorter than remaining segments put together, with numerous plumose setae. Merus tooth as long as carpus; carpus tooth is two thirds of the length of the dactylus. One plumose seta on carpus internal distal corner (Figure 2G).</p> <p>Pereopod 3 basis 0.4 of the entire length of pereopod, merus is twice the length of ischium bearing two long simple seta on medial margin, carpus has two setae on distal outer margin, carpus 1.5 times the length of merus, propodus is 0.3 of the length of carpus with a seta on distal outer margin, dactylus about one third of the length of pereopod (Figure 3E).</p> <p>Pereopod 4 basis 0.2 entire length of the pereopod, merus 2.5 times the length of ischium, carpus 1.1 times the length of merus, three setae on distal outer corner, propodus 0.4 times the length of carpus length, one seta on distal outer corner, dactylus 0.5 the length of propodus, bearing a terminal seta and a shorter one (Figure 3F).</p> <p>Pereopod 5 basis 0.3 of the entire length of the pereopod, merus 2.5 times the length of the ischium, carpus 1.5 times the length of the merus, three long setae on distal outer corner, propodus 0.2 times the length of the carpus, one seta on distal outer corner, dactylus is the same length as propodus, bearing a terminal seta the same length as dactylus (Figure 3G).</p> <p>Uropod peduncle slightly longer than rami, armed with 30 setae on inner edge, arranged in two lines from the eighth seta onward. Pleonite 6 distally rounded with two short terminal setae. Uropod exopod two-articulated with 7 plumose setae on inner edge and 6 terminal setae. Endopod two-articulated: first article with 8 setae of different sizes, with the last one being the largest; the distal part of the second article is rounded with 15 setae increasing in length from proximal to distal part and 4 terminal plumose setae (Figure 2H).</p> <p> <b>Description of the paratype ovigerous female</b> (MZB21015).</p> <p>Carapace about two times as long as deep and a fifth of the total body length. Dorsal carina armed with 6–8 teeth: the first immediately after the eyelobe, then following a gap the others close to each other. Pointed pseudorostrum. The eyelobe is elevated in lateral view, bearing a small tooth. Branchial siphon is of medium length. Anterolateral angle is rounded with a few small serrations below (Figure 5A).</p> <p>The basis length of maxilliped 3 about 0.6 times the length of the entire maxilliped, the outer process almost reaches the merus, with two long plumose setae, plus additional smaller setae on medial margin. Several plumose setae on ischium, carpus and merus distal margin. Ischium and merus longer than carpus and propodus put together. Dactylus shorter than propodus and has 3 apical setae (Figure 5B).</p> <p>Pereopod 1 basis slightly longer than the rest of limb. Merus, carpus and propodus subequal in length. The basis end bears a plumose seta reaching the merus end. Dactylus shorter than the previous 3 articles and has 5 terminal setae (Figure 5C).</p> <p>Pereopod 2 basis shorter than the other articles put together; basis, merus and carpus have plumose setae. Dactylus longer than propodus and carpus together (Figure 5D).</p> <p>Pleonite 6 distally concave, pleotelson rounded with two short terminal setae.</p> <p>Uropod peduncle slightly longer than rami, armed with 12 acuminate setae on inner edge. Rami subequal in length. Exopod two-articulated, with 8 long plumose setae and 6 terminal setae. Endopod two-articulated with proximal article shorter than distal. First article armed with 4 acuminate setae; second article armed with 9 acuminate setae increasing in length from proximal to distal, and with 2 terminal plumose setae (Figure 5E).</p> <p> <b>Remarks</b>. This new <i>Iphinoe</i> species is similar to other species within the “ <i>I. trispinosa</i> group” (sensu Ledoyer, 1965), in particular <i>I. armata</i>, <i>I. douniae</i> and <i>I. trispinosa</i>. The basis of <i>I. daphne</i> ’s pereopod 1 is longer than the remaining articles put together, differently from <i>I. armata</i>. <i>I. daphne</i> differs from <i>I</i>. <i>trispinosa</i> in the seta formula of the uropod: 10;5+ 15 in <i>I. trispinosa</i> and 12;4+ 9 in <i>I. daphne.</i> Pereopod 2 carpus of <i>I. daphne</i> presents only 1 plumose seta, whereas there are 3 in <i>I. douniae</i> and 2 in <i>I. armata</i>. Furthermore, pereopod 2 merus and carpus of <i>I. daphne</i> are shorter than in <i>I. armata,</i> as is the merus seta.</p> <p> An important diagnostic character that distinguishes <i>I. daphne</i> from other congeneric species is its sternal process: it has a distinctly bifid apex, whereas this is cup-like with 6–8 serrations in the distal border in <i>I. armata</i>. Further differences between these species are shown in synoptic Table 2. <i>I</i>. daphne and <i>I. serrata</i> both have a sternal process with a bifid apex. However in <i>I. serrata</i> the tubercle is more elongated and the tips of the apex are more divergent.</p> <p> <b>Distribution and ecology</b>. The species was only recorded in the North Adriatic basin, Area 9 (Table 4), and was not present in samples collected from similar biocenosis (SFBC or VTC) in other areas, thus suggesting that it is a Mediterranean endemic species with a restricted distributional range.</p> <p> <i>Iphinoe daphne</i> is typical of soft bottom habitats, from 3 to 15 meters deep. In our samples, this species was found in the “fine well sorted sand” (SFBC) biocenosis (with a sand percentage ranging from 69.7 to 90.6%) and had mean values of organic matter of 0.4%, but it was also found in deeper biocenosis, such as coastal terrigenous mud (VTC), with a silt and clay percentage ranging from 20% to 70% and an average value of organic matter of 1.2%.</p>Published as part of <i>Mazziotti, Cristina & Lezzi, Marco, 2020, The cumacean genus Iphinoe (Crustacea: Peracarida) from Italian waters and I. daphne n. sp. from the northwestern Adriatic Sea, Mediterranean, pp. 331-357 in Zootaxa 4766 (2)</i> on pages 338-343, DOI: 10.11646/zootaxa.4766.2.4, <a href="http://zenodo.org/record/3764096">http://zenodo.org/record/3764096</a>
Relative Energies and Geometries of the <i>cis</i>- and <i>trans</i>-HO<sub>3</sub> Radicals from the Parametric 2‑Electron Density Matrix Method
No full textThe parametric 2-electron reduced
density matrix (2-RDM) method employing the M functional [Mazziotti, D. A. Phys.
Rev. Lett. 2008, 101, 253002], also known as the 2-RDM(M) method, improves
on the accuracy of coupled electron-pair theories including coupled
cluster with single–double excitations at the computational
cost of configuration interaction with single–double excitations.
The cis- and trans-HO3 isomers along with their isomerization transition state were examined
using the recent extension of 2-RDM(M) to nonsinglet open-shell states
[Schwerdtfeger, C. A.; Mazziotti, D. A. J. Chem. Phys. 2012, 137, 034107] and several coupled cluster methods. We report the calculated energies,
geometries, natural-orbital occupation numbers, and reaction barriers
for the HO3 isomers. We find that the 2-RDM(M) method predicts
that the trans isomer of HO3 is lower in energy than the
cis isomer by 1.71 kcal/mol in the correlation-consistent polarized
valence quadruple-ζ (cc-pVQZ) basis set and 1.84 kcal/mol in
the augmented correlation-consistent polarized valence quadruple-ζ
(aug-cc-pVQZ) basis set. Results include the harmonic zero-point vibrational
energies calculated in the correlation-consistent polarized valence
double-ζ basis set. On the basis of the results of a geometry
optimization in the augmented correlation consistent polarized valence
triple-ζ basis set, the parametric 2-RDM(M) method predicts
a central oxygen–oxygen bond of 1.6187 Å. We compare these
energies and geometries to those predicted by three single-reference
coupled cluster methods and experimental results and find that the
inclusion of multireference correlation is important to describe properly
the relative energies of the cis- and trans-HO3 isomers and improve agreement with experimental geometries
Quantum Many-body Theory from a Solution of the -representability Problem
No full textHere we present a many-body theory based on a solution of the
-representability problem in which the ground-state two-particle reduced
density matrix (2-RDM) is determined directly without the many-particle wave
function. We derive an equation that re-expresses physical constraints on
higher-order RDMs to generate direct constraints on the 2-RDM, which are
required for its derivation from an -particle density matrix, known as
-representability conditions. The approach produces a complete hierarchy of
2-RDM constraints that do not depend explicitly upon the higher RDMs or the
wave function. By using the two-particle part of a unitary decomposition of
higher-order constraint matrices, we can solve the energy minimization by
semidefinite programming in a form where the low-rank structure of these
matrices can be potentially exploited. We illustrate by computing the
ground-state electronic energy and properties of the H ring
Cage versus Prism: Electronic Energies of the Water Hexamer
No full textThis document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry A, copyright © 2013 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/jp405739d.Recent experiments show that the cage isomer of the water hexamer is lower in energy than the prism isomer near 0 K, and yet state-of-the-art electronic structure calculations predict the prism to be lower in energy than the cage at 0 K. Here we study the relative energies of the water hexamers from the parametric 2-electron reduced-density-matrix (2-RDM) method in which the 2-RDM rather than the wavefunction is the basic variable of the calculations. In agreement with experiment and in contrast with traditional wavefunction methods, the 2-RDM calculations predict the cage to be more stable than the prism after vibrational zero-point correction. Multiple configurations from the hydrogen bonding are captured by the method. More generally, the results are consistent with our previous 2-RDM applications in that they reveal how multireference correlation in molecular systems is important for resolving small energy differences from hydrogen bonding as well as other types of intermolecular forces, even in systems that are not conventionally considered strongly correlated.D.A.M. gratefully acknowledges the NSF under Grant No. CHE-1152425, the ARO under Grant No. W91 INF-1 1-504 1-0085, the Keck Foundation, and Microsoft Corporation for their support.Accepted Manuscript (AM
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IDENTIFYING DIFFUSE GALAXIES THROUGH CITIZEN SCIENCE
No full textWe present a catalog of 642 diffuse galaxies (DGs) identified through a citizen science search of the Fornax cluster, of which we estimate 21.8% are nucleated. These DGs were visually identified using a combination of the Fornax Deep Survey (FDS) and Dark Energy Camera Legacy Survey (DECaLS) imaging. With the help of over 700 volunteers on Zooniverse, we examined nearly 15,000 image cutouts (spanning 26 deg^2) in 30 days, averaging 1.15 days per square degree. Our catalog recovers > 90% of the objects from prior dwarf galaxy catalogs in the parameter space explored by our search. We achieve higher completeness than existing automated detection algorithms, resulting in numerous additional detections, particularly near bright stars and galaxies. Three of the DG candidates we identify are previously undiscovered objects (in any existing search, automated or visual) that should be further investigated to determine cluster membership. A potential drop in the number density of non-nucleated DGs is observed near the cluster center. We propose that this decline may suggest a higher likelihood of forming a nuclear star cluster (NSC) via globular cluster inspiral in the cluster core. We also identify an apparent spike in the nucleated density around 400 kpc, which is not associated with any obvious structure in the cluster or in the imaging dataset and requires further investigation. The efficiency and completeness of our citizen science methodology makes it a valuable tool for mapping DG populations in future sky surveys, such as the Legacy Survey of Space and Time (LSST)
Effect of strong electron correlation on the efficiency of photosynthetic light harvesting
No full textPursuit of<i>N</i>-representability for the contracted Schrödinger equation through density-matrix reconstruction
No full text- …
