bluuebunny/crossref_metadata_2025_split huggingface dataset:
Getting the Right People to the Table
Authors: Susskind Lawrence E , Cruikshank Jeffrey L 
Published: November 2023

Abstract
The first step in consensus building is convening. The point of convening is to give the potential parties a chance to help decide who needs to be involved, and whether and how to move ahead. In this absolutely critical phase of the process, somebody has to determine whether the minimum conditions for a successful CBA effort can be met. If not, the group may have to revert to majority rule, hold its nose, and take a vote. Somebody has to perform an assessment of the conflict or issue at hand. Based on that assessment, somebody has to figure out (1) who needs to be consulted or brought to the table, and (2) how to get them there. At the same time, somebody has to begin the process of securing the resources that will be needed to conduct a full-fledged consensus-building process. By “resources,” we mean both human and financial resources. And finally, somebody has to make a judgment about whether to use CBA. We will cover all these topics in this chapter. But first, let’s look at this “somebody” who is doing, or helping to do, all these important things.
Confirming that Agreement Has Been Reached
Authors: Susskind Lawrence E , Cruikshank Jeffrey L 
Published: November 2023

Abstract
Up to this point, most of what we’ve been describing, both in general terms and in our Blaine example, has been about how to create value through deliberation. The members of the Blaine Bicentennial Committee, for example, have built upon each other’s interests to create options that otherwise wouldn’t have been possible. They have finished the difficult step of coming up with a package, and they are on the verge of deciding on a final version of that package, based on what they hear back from their respective constituencies. So is their work complete? In a word, no. Creating value is only one aspect of consensus building. Equally important is the process of distributing value. The consensus builders have planted an orchard, and it is now bearing fruit. If they have done their job well, they already have a good idea of how the fruit will be divvied up among the known constituencies.
Assigning Roles and Responsibilities
Authors: Susskind Lawrence E , Cruikshank Jeffrey L 
Published: November 2023

Abstract
At the first meeting, the group as a whole should review its roles and responsibilities. Presumably, all the participants “represent” some larger set of interested stakeholders or constituents. They may also bring special expertise to the discussion. To the extent that one of the participants is unwilling or unable to meet the expectations of the others, with regard to her representational responsibilities, it may be necessary to find a substitute. “Representation” may consist of nothing more than agreeing to serve as a go-between or a two-way channel of information.
Facilitating Group Problem Solving
Authors: Susskind Lawrence E , Cruikshank Jeffrey L 
Published: November 2023

Abstract
CBA involves not only a set of tools and techniques (like assessment and facilitation) but also a commitment to joint problem solving. Members of any organization or community are not likely to view a joint problem-solving effort as legitimate, however, unless they understand exactly who is meeting, and how well they have handled their assignments. Thus, the legitimacy of any consensus-building effort hinges in large part on the way the process is perceived by those likely to be affected by what is decided.
Molecular Schrödinger equation. II. Monte Carlo evaluation of integrals
Authors: Conroy H 
Published: November 2023

Abstract
This paper and its three companion papersa published back-to-back in the Journal of Chemical Physics describe the first variational QMC calculations for molecular systems. The first paper introduces a general form for a one-electron wavefunction along with discussions of the requirements for an accurate wavefunction and the procedure for optimization by minimizing the variance in local energies. The second, with the title given above, describes the Monte Carlo evaluation of the matrix elements required for determination of the expectation value of the energy in a variational calculation. As pointed out, Monte Carlo schemes had often been used for integrations, but there was apparently no prior report of such schemes for problems in quantum mechanics. The need for selecting points from an approximate ψ2 distribution was recognized and a procedure for doing so was proposed. In this paper and in the third and fourth papers the methods were illustrated with applications for the systems H2 +, HeH2+, HeH+, H3 2+, and H3 +. In the case of H3 + sections of potential energy surfaces were determined for linear and triangular nuclear configurations using wavefunctions with up to 29 terms. The minimum-energy structure for H3 + was found to be an equilateral triangle of side length 1.68 bohr with an energy of -1.357 hartrees, values more accurate than those of any prior calculations.
Ground state of liquid 4He
Authors: Mcmillan W L 
Published: November 2023

Abstract
One of the earliest uses of Metropolis samplinga in variational QMC calculations was not in an electronic structure problem, but in the calculation of the energy of a sample of liquid helium in which the atoms were treated as single particles. The interaction among the atoms was specified as a pairwise-additive Lennard-Jones 6-12 potential, which is a rather good approximation in this case. The trial wavefunction was a product form of the type Πi&lt;j f(rij ), with f(r) = exp [-(a1/r)a 2] and variable parameters a1 and a2 . The ground-state wavefunction for this collection of bosons is nodeless. Calculations were carried out with 32 to 108 atoms at several lattice densities in a cube with periodic boundary conditions. The energies so determined were within about 20% of the experimental values and two-body correlation functions were in reasonable agreement with those derived from x-ray data. This first variational QMC calculation for liquid helium was followed within a few years by both Green’s function and diffusion QMC calculations.
Monte-Carlo solution of Schrödinger’s equation
Authors: Grimm R C , Storer R G 
Published: November 2023

Abstract
With this paper Grimm and Storer introduced importance sampling to the field of quantum Monte Carlo. They had earlier used numerical quadrature for estimating the integrals required in evaluating energies in a diffusion-like path integral iteration scheme for solving the Schrödinger equation.0 This was extended to larger numbers of particles and higher dimensions with use of Monte Carlo methods. In conjunction with this they recognized they could take advantage of prior knowledge of the general form of a wavefunction to obtain more accurate estimates of the eigenvalue Eo .
A random-walk simulation of the Schrödinger equation:H+
3
Authors: Anderson J B 
Published: November 2023

Abstract
This paper opened the field of electronic structure calculations to quantum Monte Carlo calculations of the form originally suggested by Fermia. The system treated was the molecular ion H+ 3 which has served as a test case for new methods in quantum mechanics since about 1935. With the three protons fixed in position the problem is reduced to that of two electrons in three dimensions each. For the ground state the electrons (fermions) have opposite spins and the wavefunction is nodeless. In atomic units the Schrödinger equation in imaginary time becomes The energy obtained for the equilibrium equilateral triangle nuclear configuration was lower (but with an overlapping error bar) than the lowest-energy analytic variational result at the time and in agreement with recent predictions. The author discussed several of the questions bearing on the utility of the method, proposed the fixed-node method for incorporating the Pauli exclusion principle, and concluded that “‘In general, not enough is known for confident assessment of the merits of the method, but initial results are encouraging.”
A method to calculate vibrational frequency shifts in heteroclusters: Application to Nt-He11
Authors: Brown D F R , Gregory J K , Clary D C 
Published: November 2023

Abstract
Ionic clusters are important in a wide variety of chemical systems, especially in those involving ion-molecule reactions in the atmosphere and in biological systems, but they received relatively little attention until the mid-1990s. The Nt-Hen system is one system subjected to spectroscopic studies and theoretical examination at that time. In this paper, the authors reported diffusion QMC calculations for the vibrations within these clusters and the development of a new method for predicting the N-N vibrational frequency shifts induced by the presence of the loosely attached helium cluster Hen of varying n. Minimum-energy and vibrationally averaged structures were also reported. The QMC calculations were performed for motion on a pairwiseadditive potential energy surface fitted to ab initio electronic structure calculations. The weak coupling of the high-frequency motion of the N-N vibration with the lower frequency motions of the He atoms in the cluster allowed a separation of these motions and the treatment of the complete wavefunctions as a product of separate wavefunctions for Nt and Hen, Calculations were carried out for clusters with up to 16 helium atoms. For each of these clusters, a number of calculations were made with the N-N distance frozen. The simulations produced an adiabatic potential energy curve for N-N motion, from which vibration frequencies could be determined. The frequency shift was found to vary linearly with the number of helium atoms n. No experimental data were available for direct comparisons. The authors note the general applicability of the method to similar problems, including those of much higher complexity.
Reptation quantum Monte Carlo: A method for unbiased ground-state averages and imaginary-time correlations
Authors: Baroni S , Moroni S 
Published: November 2023

Abstract
This paper introduces a successful new method for extending diffusion QMC with importance sampling to allow the direct calculation of pure ‘¢ 2 distributions in place of mixed ‘¢ 1/Jr distributions. The method removes any bias introduced with a trial function (except that due to node locations) in the calculation of observable quantities which do not commute with the Hamiltonian. It has the advantage, relative to the descendent weighting or forward walking technique,a of a controlled walker population which reduces statistical errors. The authors have named it the reptation quantum Monte Carlo (RQMC) method. Its basic object is a path or sequence of configurations called a “reptile” which may be altered by an action called “reptation,” terms adopted from related work in the polymer area. In conventional diffusion QMC with importance sampling walkers are subjected to diffusion, drift, and a local energy-based multiplication to produce a 1/J’I/Jr distribution. Without multiplication a ‘l/Jr’l/Jr distribution is produced. In RQMC multiplication is replaced by a Metropolis rejection procedure, also based on local energies, which produces a 1/J’!/J distribution of configurations in a reptile. The generation of a new reptile, by removing the tail and adding a new head, is based on diffusion and drift for proposed moves coupled with an acceptance test. Overall, the implementation is quite similar to that for variational QMC. As described, the method was tested first for the hydrogen atom, followed by the successful demonstration of a calculation for a helium fluid, 64 4He atoms in a cubic box with periodic boundary conditions. The advantages of RQMC relative to branching diffusion QMC were pointed out for treatment of clusters, films, and superfluids as well as for estimation of electronic forces.
Relativistic calculations using Monte Carlo methods: One-electron systems
Authors: Alexander S A , Coldwell R L 
Published: November 2023

Abstract
The Schri::idinger equation is not the only fundamental equation of quantum mechanics that can be solved by Monte Carlo methods. In this paper, a solution of the four-component Dirac equation to determine relativistic energies is reported for the one-electron systems U91+, Hf, and Th 79+. The calculations were carried out in variational QMC, with trial functions optimized by minimizing the variance in local energies. For a one-electron system with more than one fixed nucleus, the four-component Dirac equation is required. The equation is similar to the Schri::idinger equation in that H’lj; = E’lj;, but the wave function is a four-component vector with individual components that may be complex, and the Hamiltonian is a 4 x 4 matrix. The exact solution for a one-electron atom is known, and the authors made use of this knowledge to show that variance minimization would produce correct coefficients in a wave function of known functional form. Thus, for U91+, the resulting energy was essentially exact. For the diatomic systems, no exact wave functions are known, and three different carefully chosen series functions of up to eight terms were investigated. Among these a mixed wave function of Slater atomic orbitals and floating Gaussian orbitals was most successful, although all three gave excellent energies. Nevertheless, for both Hf and Th 79+, the energies were slightly higher than the best available estimates from other methods of calculation. Properties other than the energy could be evaluated in a similar fashion using the optimized wave functions, and additional terms could be added to the Hamiltonian.
On the accuracy of the fixed-node diffusion quantum Monte Carlo method
Authors: Manten S , Lüchow A 
Published: November 2023

Abstract
In this work Manten and Liichow assessed the accuracy of allelectron fixed-node diffusion QMC calculations with nodes taken from Hartee-Fock wavefunctions with high-quality basis sets. The electronic energies associated with 17 different reactions involving a total of 20 small molecules were determined and compared with experimental values and with those calculated by Klopper et al.a using the coupled cluster method CCSD(T) with correlation consistent basis sets cc-pVDZ and cc-pVTZ. The molecules involved were limited to those containing the atoms H, C, 0, N, and F. Typical reactions were H2CO + 2H2 --+ CH4 + H2O and H2O + F --+ HOF + H. The geometries for the QMC calculations were optimized with MP2/cc-pVTZ calculations. The QMC total energies for the 20 molecules were lower than CCSD(T) values, but only valence electrons were correlated in the CCSD(T) calculations. Node location error was approximately 0.0015 hartrees for the C, N, 0, and F atoms and their hydrides, but substantial cancellation of node error is to be expected in determining enthalpy changes for reactions.
Role of electronic correlation in the Si(lOO) reconstruction: A quantum Monte Carlo study
Authors: Healy S B , Filippi C , Kratzer, P , Penev E , Scheffler M 
Published: November 2023

Abstract
The 100 surface of a silicon crystal is believed to reconstruct to form rows of silicon dimers in either a “symmetric” pattern ( 11 I 111 I I) or a somewhat deformed “buckled” pattern (/\/\/\/\) in which the dimers are twisted alternately within each row. At room temperature the dimers may flip back and forth between configurations and they appear symmetric in scanning tunneling microscopy. Below 120 K the buckled configuration appears, but below 20 K the symmetric configuration has been indicated but might be due to flipping, and arguments in favor of each of the configurations have been made. Theoretical work is equivocal. Density functional (DFT) calculations favor the buckled configuration. Multiconfiguration self-consistent field (MCSCF) and configuration interaction (CI) calculations favor the symmetric. The indicated differences in energies for the two structures are small, and electron correlation (note the title) is thus expected to be important in determining the minimum-energy structure. Diffusion QMC provides the required accurate description of correlation for large systems. As in the earlier studies with other methods the authors treated the model systems Si9H12, Sii5H16, and Si21H20 - clusters which have one, two, and three dimers in configurations like those on the Si(lO0) surface. The calculations were made using silicon pseudopotentials tested in calculations for Si2. For the intermediate cluster the energies of the symmetric and the buckled configurations were nearly identical. For the larger cluster, with three dimers, the buckled configuration was favored by 0.34(6) eV or 0.11(2) eV per dimer. This energy difference is similar to that for DFT calculations (LDA to B3LYP). The agreement suggests that the dynamic correlation effects, described better in DQMC and DFT than in MCSCF and CI, are important. The buckled configuration is thus to be favored, but many questions in both theory and experiment remain unresolved for this system.
Quantum Monte Carlo study of the three- to one-dimensional crossover for a trapped Bose gas
Authors: Astrakharchik G E , Giorgini S 
Published: November 2023

Abstract
These two papers, published back to back, provide superb examples of the use of a quantum Monte Carlo method to obtain exact solutions for a problem difficult to treat by other methods. The problem is that of a bosonic atomic gas confined in a cigarshaped trap. As the cigar is narrowed the atoms are less able to pass each other, their behavior approaches that of fermions, and they are said to exhibit “fermionization.” Using diffusion QMC the authors were able to determine the ground-state energies, examine structural properties, confirm that fermionization can occur, and predict conditions under which it might be observed. The calculations by Blume were carried out for 2-20 atoms confined in axially symmetric traps of varied aspect ratios. The confining potential for each atom was given by Vk = CpPl + Czzl (radial and axial positions squared). The atom-atom interactions were simple hard-sphere potentials. The (nodeless) guided diffusion calculations used a trial wave function of the Jastrow type, a product of atom-trap terms and atom-atom terms. The calculations by Astrakharchik and Giorgini were carried out similarly but included both hard and soft spheres with numbers in the range of 5 to 100 atoms. Comparisons were made with predictions of the Lieb Liniger equation of state.
Quantum Monte Carlo calculations of neutron matter
Authors: Carlson J , Morales J , Pandharipande V R , &gt;Ravenhall D E 
Published: November 2023

Abstract
Pure neutron matter is not likely to be found in any of the Earth’s laboratories, but it has been found to exist as the material of neutron stars. It presents an interesting and difficult manybody problem which may be attacked by QMC methods. In this paper the authors report variational, approximate fixed-node, and released-node QMC calculations for uniform neutron matter in a three-dimensional box with periodic boundary conditions. These allow the determination of the energy E(p) as a function of the neutron density p for a realistic two-neutron interaction expression. The results are used to assess the accuracy of earlier variational approaches. The system treated was that of 14 neutrons in a cube at densities in the range of 1 / 4 to 3/2 the density p0 typical for nuclear matter. Most of the calculations were done for the Argonne v8’ two-body interaction potential. The trial wavefunction was a correlated Slater function, identical for the variational and diffusion calculations, specifying the nodes and used in importance sampling. Corrections were made for the effects of finite box dimensions. The released-node calculations were limited to very short time intervals especially for the higher densities. The energies E(p) found in the diffusion QMC calculations were 5 to 10% lower than those of the variational QMC. The releasednode results, with relatively large statistical errors, were not significantly different from the fixed-node results. The energies determined for the lower densities were estimated to be accurate within 2% and those for the higher densities somewhat less accurate. The results showed earlier predictions to be generally correct. Comparisons of results from variational chain summations (VCS) indicated an overall accuracy of about 10% for that method.
Rotational dynamics of CO solvated in small He clusters: A quantum Monte Carlo study
Authors: Cazzato P , Paolini S , Moroni S , Baroni S 
Published: November 2023

Abstract
The reptation QMC method introduced by Baroni and Moroni0 a few years earlier is demonstrated in this paper to be the method of choice for predicting the rotational-vibrational features of the infrared spectrum of CO in small helium droplets. The calculations gave good agreement with experimental measurements for these relatively complex systems and provided insights into some of their characteristics not observable in experiments. The calculations were carried out for clusters containing one CO molecule and up to 30 He atoms. The CO molecule was treated as rigid, and HeHe and He-CO interactions were treated as pairwise additive, with pair terms from ab initio calculations. The trial wavefunction for this nodeless bosonic system was a Jastrow function made up of exponential functions dependent on the CO distance and orientation with respect to He atom and He-He distances. The reptation QMC calculations were carried out as diffusion QMC calculations with importance-sampling drift, but without multiplication so that the energy obtained was the expectation value of the energy for the trial wavefunction. The reptation part of the calculation produced exact (or nearly exact) expectation values and, more important in these calculations, unbiased quantum correlation functions from which the absorption spectra of the CO molecule could be determined. The results exhibit a variety of interesting phenomena. The binding energy for an additional atom first increases and then decreases before leveling out with increasing cluster size. The calculated rotational absorption spectra show two types of lines, one increasing in strength with cluster size, the other decreasing with cluster size. Much more detail, especially in regard to the droplet shape, revealed in the calculations.
Interpretation of Hund’s multiplicity rule for the carbon atom
Authors: Hongo K , Maezono R , Kawazoe Y , Towler M D , Needs R J 
Published: November 2023

Abstract
Originating from experimental observations and published in 1925, Hund’s rulea states that the electronic state with the lowest energy is the one with the highest spin multiplicity S. Obeyed by most atoms and molecules, although exceptions are known, the rule has been explained (incorrectly) as due to the lower average electron-electron repulsion flee for electrons of the same spin in higher S states, and (correctly)b as due to lowering of the electron nucleus energy Ven aselectrons of the same spin avoid each other and can move closer to the nucleus. The authors call this Boyd’s less screeningc mechanism. A completely satisfactory analysis of the phenomenon requires very accurate wavefunctions, and in this paper the authors used VQMC and DQMC calculations to provide those wavefunctions for singlet and triplet states of the carbon atom.