FRANCIS NORMAN C. PARAAN
University of the Philippine Diliman
Sex: Male
Education:
Doctor of Philosophy in Physics, Stony Brook University, New York
Field of Specialization:
Quantum Physics
Computational Physics
Condensed Matter Physics
Researches:
Article title: Selective capture of CO2 over N2 and CH4: B clusters and their size effects
Authors: Alexandra B Santos-Putungan, Nataša Stojić, Nadia Binggeli, Francis NC Paraan
Publication title: Materials Today Communications 22:100712, March 2020
Abstract:
Using density-functional theory (DFT), we investigate the selectivity of adsorption of CO2 over N2 and CH4 on planar-type B clusters, based on our previous finding of strong chemisorption of CO2 on the B10−13 planar and quasiplanar clusters. We consider the prototype B8 and B12 planar-type clusters and perform a comparative study of the adsorption of the three molecules on these clusters. We find that, at room temperature, CO2 can be separated from N2 by selective binding to the B12 cluster and not to the B8 cluster. Selective adsorption of CO2 over CH4 at room temperature is possible for both clusters. Based on our DFT-adsorption data (including also a semi-infinite Boron sheet) and the available literature-adsorption value for N2 on the planar-type B36 cluster, we discuss the selectivity trend of CO2 adsorption over N2 and CH4 with planar-cluster size, showing that it extends over sizes including B10-13 clusters and significantly larger.
Article title: Strong chemisorption of CO2 on B10-B13 planar-type clusters
Authors: Alexandra B Santos-Putungan, Nataša Stojić, Nadia Binggeli, Francis NC Paraan
Publication title: Journal of Physics: Condensed Matter 31:14, January 2019
Abstract:
An ab initio density functional study was performed investigating the adsorption of CO$_2$ on the neutral boron B$_{n}$ ($n = 10-13$) clusters, characterized by planar and quasiplanar ground-state atomic structures. For all four clusters, we found strong chemisorption energy of CO$_2$ reaching 1.6 eV for B$_{12}$ at the cluster edge sites with the adsorbed molecule in the plane of the cluster. A configuration with chemisorbed dissociated CO$_2$ molecule also exists for B$_{11}$ and B$_{13}$ clusters. The strong adsorption is due to the bending of the CO$_2$ molecule, which provides energetically accessible fully in-plane frontier molecular orbitals matching the edge states of the clusters. At the same time, the intrinsic dipole moment of a bent CO$_2$ molecule facilitates the transfer of excess electronic charge from the cluster edges to the molecule.
Article title: Controlling the nucleophilic properties of cobalt salen complexes for carbon dioxide capture
Authors: Meliton R Chiong, Francis NC Paraan
Publication title: RSC advances 9(40): 23254-23260, January 2019
Abstract:
The nucleophilic properties of cobalt salen complexes are examined using density functional theory to investigate its carbon fixing capacity.
Full text link : https://tinyurl.com/y72u3qqq
Article title: Average work done in a ground state quantum quench of the Kitaev chain model with variable-range interactions
Authors: Francis N. C. Paraan, Raymart Jay Canoy
Conference title: 36th Samahang Pisika ng Pilipinas Physics Conference and Annual Meeting
At: Puerto Princesa City, Palawan, Philippine
Abstract:
We study the average work done associated with a ground state quantum quench of the Kitaev chain model with variable-range interactions. We do this by initially preparing an isolated quantum system in the ground state of the initial Hamiltonian at zero temperature. We, then, abruptly change the relative chemical potential parameter. The average work done on the system, which is defined as the difference between the measured energies before and after the quench, is derived and shown to have inflection points at the critical values of the relative chemical potential of the initial Hamiltonian.
Full text link: https://tinyurl.com/y7etbfyb
Article title: Ab initio study on the binding of carbon dioxide to cobalt salen complex
Authors: Meliton Chiong III, Francis N. C. Paraan
Conference title: 35th Samahang Pisika ng Pilipinas Physics Conference and Annual Meeting
At: Cebu City
Abstract:
Metal-organic complexes, such as metal-Schiff bases, can function as catalysts for electrochemical reduction. In this work we present first principles electronic structure calculations for the adduct formation involving carbon dioxide (CO2) and cobalt salen [Co(salen)] complex. Binding energy calculations show that carbon dioxide forms a stable adduct with [Co(salen)] −1 complex. The bonding between carbon dioxide and the cobalt metal center involves back-bonding mainly between the metal d z 2 orbital and the π * orbital of CO2. An accompanying partial charge transfer from Co to CO2 was observed. This study can be used as a preliminary result to further study the structure and stability of other cobalt-carbon complexes.
Article title: Simple techniques for improving deep neural network outcomes on commodity hardware
Authors: Nicholas Christopher A. Colina, Carlos E. Perez, Francis N. C. Paraan
Conference title: STRUCTURE, FUNCTION AND DYNAMICS FROM NM TO GM: Proceedings of the 8th Jagna International Workshop
Abstract:
We benchmark improvements in the performance of deep neural networks (DNN) on the MNIST data test upon imple-menting two simple modifications to the algorithm that have little overhead computational cost. First is GPU parallelization on a commodity graphics card, and second is initializing the DNN with random orthogonal weight matrices prior to optimization. Eigenspectra analysis of the weight matrices reveal that the initially orthogonal matrices remain nearly orthogonal after training. The probability distributions from which these orthogonal matrices are drawn are also shown to significantly affect the performance of these deep neural networks.
Article title: Integer effects in the entanglement and spin fluctuations of a quantum Hall system with Rashba interactions
Authors: Rona Barbarona, Francis N. C. Paraan
Publication title: Journal of Statistical Mechanics: Theory and Experiment 2016(5): 053104, May 2016
Abstract:
We report distinct nonanalytic signatures in the spin-orbit entanglement of a 2D electron gas with Rashba interactions at integer values of the filling factor and at certain level crossings. The accompanying sharp changes in the bulk spin-orbit entanglement entropy can be probed by measuring the fluctuation in the transverse spin polarization of the electron gas.
Article title: Entanglement-fluctuation relation for bipartite pure states
Authors: Aura Mae B Villaruel, Francis NC Paraan
Publication title: Physical Review A 94(2): 022323, December 2015
Abstract:
We identify a subsystem fluctuation (variance) that measures entanglement in an arbitrary bipartite pure state. This fluctuation is of an observable that generalizes the notion of polarization to an arbitrary N-level subsystem. We express this polarization fluctuation in terms of the order-2 Renyi entanglement entropy and a generalized concurrence. The fluctuation-entanglement relation presented here establishes a framework for experimentally measuring entanglement using Stern-Gerlach-type state selectors.
Full text link: https://arxiv.org/pdf/1512.05551.pdf
Article title: Exact work statistics of quantum quenches in the anisotropic XY model
Authors: Francis A Bayocboc Jr, Francis NC Paraan
Publication title: Physical Review E 92(3): 032142, September 2015
Abstract:
We derive exact analytic expressions for the average work done and work fluctuations in instantaneous quenches of the ground and thermal states of a one-dimensional anisotropic XY model. The average work and a quantum fluctuation relation is used to determine the amount of irreversible entropy produced during the quench, eventually revealing how the closing of the excitation gap leads to increased dissipated work. The work fluctuation is calculated and shown to exhibit non-analytic behavior as the pre-quench anisotropy parameter and transverse field are tuned across quantum critical points. Exact compact formulas for the average work and work fluctuation in ground state quenches of the transverse field Ising model allow us to calculate the first singular derivative at the critical field values.
Article title: Effective thermodynamics of isolated entangled squeezed and coherent states
Authors: King Karl R Seroje, Rafael S. dela Rosa, Francis NC Paraan
Publication title: European Journal of Physics 36(5): 0550551, August 2015
Abstract:
The R\'enyi entanglement entropy is calculated exactly for mode-partitioned isolated systems such as the two-mode squeezed state and the multi-mode Silbey-Harris polaron ansatz state. Effective thermodynamic descriptions of the correlated partitions are constructed to present quantum information theory concepts in the language of thermodynamics. Boltzmann weights are obtained from the entanglement spectrum by deriving the exact relationship between an effective temperature and the physical entanglement parameters. The partition function of the resulting effective thermal theory can be obtained directly from the single-copy entanglement.
Full text link: https://tinyurl.com/y9cfktv4
Article title: Entanglement spectrum and number fluctuations in the spin-partitioned BCS ground state
Authors: Xavier M Puspus, Kristian Hauser Villegas, Francis NC Paraan
Publication title: Physical Review B 90(15): 155123, October 2014
Abstract:
We study entanglement between the spin components of the Bardeen-Cooper-Schrieffer (BCS) ground state by calculating the full entanglement spectrum and the corresponding von Neumann entanglement entropy. The entanglement spectrum is effectively modeled by a generalized Gibbs ensemble (GGE) of non-interacting electrons, which may be approximated by a canonical ensemble at the BCS critical temperature. We further demonstrate that the entanglement entropy is jointly proportional to the pairing energy and to the number of electrons about the Fermi surface (an area law). Furthermore, the entanglement entropy is also proportional to the number fluctuations of either spin component in the BCS state.
Full text link: https://tinyurl.com/y9ggn7b6
Article title: Quantum phase transition in a multicomponent anyonic Lieb-Liniger model
Authors: Raul A Santos, Francis NC Paraan, Vladimir E Korepin
Publication title: Physical Review B 86(4), April 2012
Abstract:
We study a one-dimensional multicomponent anyon model that reduces to a multicomponent Lieb-Liniger gas of impenetrable bosons (Tonks-Girardeau gas) for vanishing statistics parameter. At fixed component densities, the coordinate Bethe ansatz gives a family of quantum phase transitions at special values of the statistics parameter. We show that the ground state energy changes extensively between different phases. Special regimes are studied and a general classification for the transition points is given. An interpretation in terms of statistics of composite particles is proposed.
Full text link: https://tinyurl.com/y8j7zt8v
Article title: Entanglement spectra of q-deformed higher spin VBS states
Authors: Raul A Santos, Francis NC Paraan, Vladimir E Korepin, Andreas Klümper
Publication title: Journal of Physics A: Mathematical and Theoretical 45(17), January 2012
Abstract:
We calculate the reduced density matrix of a block of integer spin-S's in a q-deformed valence-bond-solid (VBS) state. This matrix is diagonalized exactly for an infinitely long block in an infinitely long chain. We construct an effective Hamiltonian with the same spectrum as the logarithm of the density matrix. We also derive analytic expressions for the von Neumann and R\'enyi entanglement entropies. For blocks of finite length, we calculate the eigenvalues of the reduced density matrix by perturbation theory and numerical diagonalization. These results enable us to describe the effects of finite-size corrections on the entanglement spectrum and entropy in this generalized VBS model.
Full text link: https://tinyurl.com/yavqtfer
Article title: Entanglement spectra of the q-deformed Affleck-Kennedy-Lieb-Tasaki model and matrix product states
Authors: RA Santos, FNC Paraan, VE Korepin, A Klümper
Publication title: EPL (Europhysics Letters) 98(3): 37005, December 2011
Abstract:
We exactly calculate the reduced density matrix of matrix product states (MPS). Our compact result enables one to perform analytic studies of entanglement in MPS. In particular, we consider the MPS ground states of two anisotropic spin chains. One is a q-deformed Affleck-Kennedy-Lieb-Tasaki (AKLT) model and the other is a general spin-1 quantum antiferromagnet with nearest-neighbor interactions. Our analysis shows how anisotropy affects entanglement on different continuous parameter manifolds. We also construct an effective boundary spin model that describes a block of spins in the ground state of the q-deformed AKLT Hamiltonian. The temperature of this effective model is given in terms of the deformation parameter q.
Full text link: https://tinyurl.com/ydzbcmxc
Article title: Erratum: Entanglement in bipartite pure states of an interacting boson gas obtained by local projective measurements [Phys. Rev. A 84 , 032330 (2011)]
Authors: Francis NC Paraan, Javier Molina-Vilaplana, Vladimir E Korepin, Sougato Bose
Publication title: Physical Review A 86(4): 049901, September 2011
Abstract:
We quantify the extractable entanglement of excited states of a Lieb-Liniger gas that are obtained from coarse-grained measurements on the ground state in which the boson number in one of two complementary contiguous partitions of the gas is determined. Numerically exact results obtained from the coordinate Bethe ansatz show that the von Neumann entropy of the resulting bipartite pure state increases monotonically with the strength of repulsive interactions and saturates to the impenetrable-boson limiting value. We also present evidence indicating that the largest amount of entanglement can be extracted from the most probable projected state having half the number of bosons in a given partition. Our study points to a fundamental difference between the nature of the entanglement in free-bosonic and free-fermionic systems, with the entanglement in the former being zero after projection, while that in the latter (corresponding to the impenetrable-boson limit) being nonzero.
Full text link: https://tinyurl.com/y6w8n3ks
Article title: Perturbative correction to the ground state properties of one-dimensional strongly interacting bosons in a harmonic trap
Authors: Francis NC Paraan, Vladimir E Korepin
Publication title: Physical Review A 82(6) November 2010
Abstract:
We calculate the first-order perturbation correction to the ground state energy and chemical potential of a harmonically trapped boson gas with contact interactions about the infinite repulsion Tonks-Girardeau limit. With $c$ denoting the interaction strength, we find that for a large number of particles $N$ the $1/c$ correction to the ground state energy increases as $N^{5/2}$, in contrast to the unperturbed Tonks-Girardeau value that is proportional to $N^2$. We describe a thermodynamic scaling limit for the trapping frequency that yields an extensive ground state energy and reproduces the zero temperature thermodynamics obtained by a local density approximation.
Full text link: https://tinyurl.com/ycwrdz4e
Article title: Quantum quenches in the Dicke model: Statistics of the work done and of other observables
Authors: Francis NC Paraan, Alessandro Silva
Publication title: Physical Review E 80(6), December 2009
Abstract:
We study the statistics of the work done in a zero temperature quench of the coupling constant in the Dicke model describing the interaction between an ensemble of two level systems and a single bosonic mode. When either the final or the initial coupling constants approach the critical coupling lambdac that separates the normal and superradiant phases of the system, the probability distribution of the work done displays singular behavior. The average work tends to diverge as the initial coupling parameter is brought closer to the critical value lambdac. In contrast, for quenches ending close to criticality, the distribution of work has finite moments but displays a sequence of edge singularities. This contrasting behavior is related to the difference between the processes of compression and expansion of a particle subject to a sudden change in its confining potential. We confirm this by studying in detail the time-dependent statistics of other observables, such as the quadratures of the photons and the total occupation of the bosonic modes.
Full text link: https://tinyurl.com/y7h5pnnk
Article title: Brownian motion of a charged particle driven internally by correlated noise
Authors: Francis NC Paraan, Mikhail P Solon, JP Esguerra
Publication title: Physical Review E 77(2), March 2008
Abstract:
We give an exact solution to the generalized Langevin equation of motion of a charged Brownian particle in a uniform magnetic field that is driven internally by an exponentially correlated stochastic force. A strong dissipation regime is described in which the ensemble-averaged fluctuations of the velocity exhibit transient oscillations that arise from memory effects. Also, we calculate generalized diffusion coefficients describing the transport of these particles and briefly discuss how they are affected by the magnetic field strength and correlation time. Our asymptotic results are extended to the general case of internal driving by correlated Gaussian stochastic forces with finite autocorrelation times.
Full text link: https://tinyurl.com/yathf6pz
Article title: Exact moments in a continuous time random walk with complete memory of its history
Authors: Francis NC Paraan, JP Esguerra
Publication title: Physical Review E 74(3), October 2006
Abstract:
We present a continuous time generalization of a random walk with complete memory of its history [Phys. Rev. E 70, 045101(R) (2004)] and derive exact expressions for the first four moments of the distribution of displacement when the number of steps is Poisson distributed. We analyze the asymptotic behavior of the normalized third and fourth cumulants and identify new transitions in a parameter regime where the random walk exhibits superdiffusion. These transitions, which are also present in the discrete time case, arise from the memory of the process and are not reproduced by Fokker-Planck approximations to the evolution equation of this random walk.
Full text link: https://tinyurl.com/y88oj3dd