ORCID Profile
0000-0002-7961-7016
Current Organisations
European Association of Urology
,
University of Catania
,
Virginia Tech
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Publisher: AIP Publishing
Date: 28-10-2012
DOI: 10.1063/1.4759075
Abstract: The crystal structures for the three perovskites, CaSnO3, YAlO3, and LaAlO3, were geometry optimized at the density functional theory level for a wide range of simulated isotropic pressures up to 80 GPa. The connections between the geometry optimized bond lengths, R(M-O), the values of the electron density, ρ(rc), the local kinetic, G(rc), potential, V(rc), energy densities, H(rc), and the Laplacian, ∇2(rc), at the bond critical points, rc, for the M-O nonequivalent bonded interactions were examined. With increasing pressure, ρ(rc) increases along four distinct trends when plotted in terms of the Al-O, Ca-O, Sn-O, Y-O, and La-O bond lengths, but when the bond lengths were plotted in terms of ρ(rc)/r where r is the periodic table row number of the M atoms, the data scatter along a single trend modeled by the power law regression expression R(M-O) = 1.41(ρ(rc)/r)−0.21, an expression that is comparable with that obtained for the bonded interactions for a large number of silicate and oxides crystals, R(M-O) = 1.46(ρ(rc)/r)−0.19 and that obtained for a relatively large number of hydroxyacid molecules R(M-O) = 1.39(s/r)−0.22 where s is the Pauling bond strength of a bonded interaction. The similarity of the expressions determined for the perovskites, silicate and oxides crystals, and hydroxyacid molecules suggest that the bonded interactions in molecules and crystal are not only similar and comparable. The close correspondence of the expressions for the perovskites, the silicate and oxide crystals, and the molecules indicates that Pauling bond strength and ρ(rc) are comparable measures of the bonded interactions, the larger the accumulation of the electron density between the bonded atoms the larger the value of s, the shorter the bond lengths. It also indicates that the bonded interactions that govern the bond length variations behave as if largely short ranged. Like ρ(rc)/r, the values of G(rc)/r, V(rc)/r, ∇2(rc)/r likewise correlate in terms of R(M-O) in a single trend. With increasing pressure, the value of V(rc) decreases at a faster rate than G(rc) increases consistent with the observation that ρ(rc) increases with increasing pressure thereby stabilizing the structures at high pressures. As evinced by the well-developed power law trends between R(M-O) and the bond critical point properties, the bulk of the bonded interactions for the perovskites are concluded to change progressively from closed-shell to intermediate polar covalent interactions with increasing pressure. A well-developed trend between the ratios |V(rc)| /G(rc) and H(rc)/ρ(rc) is consistent with this conclusion. The employment of a positive value for the Laplacian alone in distinguishing between closed shell and polar covalent bonded interactions is unsatisfactory when 2G(rc) & |V(rc)| & G(rc).
Publisher: American Chemical Society (ACS)
Date: 20-07-2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CP02827A
Abstract: In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method developers and practitioners.
Publisher: American Chemical Society (ACS)
Date: 20-07-2022
Publisher: American Chemical Society (ACS)
Date: 09-03-2023
Publisher: Korean Society for Sexual Medicine and Andrology
Date: 2022
DOI: 10.5534/WJMH.220048
Abstract: Varicocele is a common problem among infertile men. Varicocele repair (VR) is frequently performed to improve semen parameters and the chances of pregnancy. However, there is a lack of consensus about the diagnosis, indications for VR and its outcomes. The aim of this study was to explore global practice patterns on the management of varicocele in the context of male infertility. Sixty practicing urologists/andrologists from 23 countries contributed 382 multiple-choice-questions pertaining to varicocele management. These were condensed into an online questionnaire that was forwarded to clinicians involved in male infertility management through direct invitation. The results were analyzed for disagreement and agreement in practice patterns and, compared with the latest guidelines of international professional societies (American Urological Association [AUA], American Society for Reproductive Medicine [ASRM], and European Association of Urology [EAU]), and with evidence emerging from recent systematic reviews and meta-analyses. Additionally, an expert opinion on each topic was provided based on the consensus of 16 experts in the field. The questionnaire was answered by 574 clinicians from 59 countries. The majority of respondents were urologists/uro-andrologists. A wide ersity of opinion was seen in every aspect of varicocele diagnosis, indications for repair, choice of technique, management of sub-clinical varicocele and the role of VR in azoospermia. A significant proportion of the responses were at odds with the recommendations of AUA, ASRM, and EAU. A large number of clinical situations were identified where no guidelines are available. This study is the largest global survey performed to date on the clinical management of varicocele for male infertility. It demonstrates: 1) a wide disagreement in the approach to varicocele management, 2) large gaps in the clinical practice guidelines from professional societies, and 3) the need for further studies on several aspects of varicocele management in infertile men.
Publisher: American Chemical Society (ACS)
Date: 18-03-2021
Publisher: American Chemical Society (ACS)
Date: 18-07-2019
Publisher: American Chemical Society (ACS)
Date: 13-01-2022
Publisher: American Chemical Society (ACS)
Date: 12-01-2023
Publisher: American Chemical Society (ACS)
Date: 18-07-2019
Publisher: American Chemical Society (ACS)
Date: 20-07-2022
Publisher: XMLink
Date: 2023
DOI: 10.5534/WJMH.230008
Publisher: American Chemical Society (ACS)
Date: 18-07-2019
Publisher: American Chemical Society (ACS)
Date: 18-03-2021
Publisher: AIP Publishing
Date: 22-11-2006
DOI: 10.1063/1.2388260
Abstract: Vertical and adiabatic excitation energies of the lowest A′2 excited state in the water-hydroxyl complex have been determined using coupled cluster, multireference configuration interaction, multireference perturbation theory, and density-functional methods. A significant redshift of about 0.4eV in the vertical excitation energy of the complex compared to that of the hydroxyl radical monomer is found with the coupled cluster calculations validating previous results. Electronic excitation leads to a structure with near-equal sharing of the hydroxyl hydrogen by both oxygen atoms and a concomitantly large redshift of the adiabatic excitation energy of approximately 1eV relative to the vertical excitation energy. The combination of redshifts ensures that the electronic transition in the complex lies well outside the equivalent excitation in the hydroxyl radical monomer. The complex is approximately five times more strongly bound in the excited state than in the ground state.
Publisher: American Chemical Society (ACS)
Date: 18-07-2019
Publisher: American Chemical Society (ACS)
Date: 16-03-2023
Publisher: American Chemical Society (ACS)
Date: 14-04-2022
Publisher: American Chemical Society (ACS)
Date: 12-01-2023
Publisher: American Chemical Society (ACS)
Date: 14-01-2021
Publisher: American Chemical Society (ACS)
Date: 16-03-2023
Publisher: American Chemical Society (ACS)
Date: 14-04-2022
Publisher: American Chemical Society (ACS)
Date: 14-01-2021
Publisher: American Chemical Society (ACS)
Date: 14-01-2021
Publisher: Wiley
Date: 31-10-2011
DOI: 10.1002/WCMS.93
Publisher: American Chemical Society (ACS)
Date: 20-01-2022
Publisher: American Chemical Society (ACS)
Date: 18-03-2021
Publisher: AIP Publishing
Date: 13-05-2020
DOI: 10.1063/5.0006002
Abstract: PSI4 is a free and open-source ab initio electronic structure program providing implementations of Hartree–Fock, density functional theory, many-body perturbation theory, configuration interaction, density cumulant theory, symmetry-adapted perturbation theory, and coupled-cluster theory. Most of the methods are quite efficient, thanks to density fitting and multi-core parallelism. The program is a hybrid of C++ and Python, and calculations may be run with very simple text files or using the Python API, facilitating post-processing and complex workflows method developers also have access to most of PSI4’s core functionalities via Python. Job specification may be passed using The Molecular Sciences Software Institute (MolSSI) QCSCHEMA data format, facilitating interoperability. A rewrite of our top-level computation driver, and concomitant adoption of the MolSSI QCARCHIVE INFRASTRUCTURE project, makes the latest version of PSI4 well suited to distributed computation of large numbers of independent tasks. The project has fostered the development of independent software components that may be reused in other quantum chemistry programs.
Publisher: American Chemical Society (ACS)
Date: 14-04-2022
Publisher: XMLink
Date: 2023
DOI: 10.5534/WJMH.220282
Publisher: American Chemical Society (ACS)
Date: 12-01-2023
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2022
Publisher: American Chemical Society (ACS)
Date: 13-01-2022
Publisher: XMLink
Date: 2023
DOI: 10.5534/WJMH.230076
Publisher: American Chemical Society (ACS)
Date: 13-01-2022
No related grants have been discovered for Thomas Crawford.