@article { ISI:000241168600010, title = {Constrained variational response to Fock-space multi-reference coupled-cluster theory: Some pilot applications}, journal = {Journal of Molecular Structure-Theochem}, volume = {768}, number = {1-3}, year = {2006}, month = {AUG}, pages = {91-96}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Fock space (FS) multi-reference (MR) coupled-cluster (CC) has been established to be state-of-the-art method for energies of open-shell radicals, ionized, electron attached states and excited states. Due to the multi-root nature of the method, the linear response of MRCC, however, is non-trivial. Constrained variation approach (CVA) makes it plausible to calculate response of the MRCC method efficiently. However, the approach is used for only one root of the problem at a time. In the present article, we make first implementation of the approach and present test results of dipole moments of small radicals. (c) 2006 Elsevier B.V. All rights reserved.

}, keywords = {constrained variation, coupled-cluster, Dipole moment, Multi-reference, response}, issn = {0166-1280}, doi = {10.1016/j.theochem.2006.05.022}, author = {Manohar, Prashant Uday and Vaval, Nayana and Pal, Sourav} } @conference { ISI:000252146200027, title = {Constrained variational response to fock-space multi-reference coupled-cluster theory: formulation for excited-state electronic structure calculations and some pilot applications}, booktitle = {Computational Methods in Science and Engineering Vol 1: Theory and Computation: Old Problems and New Challenges}, series = {AIP CONFERENCE PROCEEDINGS}, volume = {963}, year = {2007}, note = {International Conference on Computational Methods in Science and Engineering, Corfu, GREECE, SEP 25-30, 2007}, month = {SEP}, pages = {337-344}, publisher = {European Soc Computat Methods Sci \& Engn; Minist Natl Educ \& Religious Affairs; E4 Comp Engn}, organization = {European Soc Computat Methods Sci \& Engn; Minist Natl Educ \& Religious Affairs; E4 Comp Engn}, address = {2 Huntington Quadrangle, Ste 1no1, Melville, NY 11747-4501 USA}, abstract = {

Fock-space (FS) multi-reference (MR) coupled-cluster (CC) method has emerged as compact tool to account for electronic structure of open-shell systems and molecules in low-lying excited states. Development of linear response (LR) has been one of the challenging problems in FSMRCC due to multiple-root nature of effective Hamiltonian. The recently developed constrained variational approach (CVA) has opened up a promising tool for efficient evaluation of analytic response properties. In this article, we present formulation of the method for excited state calculations. We discuss the decoupling of equations as a result of spin-adaptation and present some preliminary results for analytical dipole moments and polarizabilities of some molecules in low-lying triplet excited states.

}, keywords = {CVA, Dipole moment, excited states, FSMRCC, polarizability}, isbn = {978-0-7354-0477-9}, issn = {0094-243X}, author = {Manohar, Prashant Uday and Pal, Sourav}, editor = {Maroulis, G and Simos, TE} } @article { ISI:000259876700012, title = {Calculation of vibrational energy of molecule using coupled cluster linear response theory in bosonic representation: convergence studies}, journal = {Journal of Chemical Physics}, volume = {129}, number = {13}, year = {2008}, month = {OCT}, pages = {134111}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {

Vibrational excited state energies have been calculated using vibrational coupled cluster linear response theory (CCLRT). The method has been implemented on formaldehyde and water molecule. Convergence studies have been shown with varying the cluster operator from S(4) to S(6) as well as the excitation operator from four bosons to six bosons. A good agreement with full configuration interaction results has been observed with S(6) truncation at coupled-cluster method level and six bosonic excitations at CCLRT level. (C) 2008 American Institute of Physics.

}, issn = {0021-9606}, doi = {10.1063/1.2982502}, author = {Banik, Subrata and Pal, Sourav and Prasad, M. Durga} } @article { ISI:000253511900004, title = {Comparative study of structural, acidic and hydrophilic properties of Sn-BEA with Ti-BEA using periodic density functional theory}, journal = {Journal of Physical Chemistry B}, volume = {112}, number = {9}, year = {2008}, month = {MAR}, pages = {2573-2579}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Periodic density functional theory has been employed to characterize the differences in the structural, Lewis acidic and hydrophilic properties of Sn-BEA and Ti-BEA. We show that the incorporation of Sri increases the Lewis acidity of BEA compared to the incorporation of Ti. Hence, the present work gives insight into the role of Sn in increasing the efficiency of the oxidation reactions. The results also justify that the percentage of Sri substituted in BEA is less than Ti. The structural analysis shows that the first coordination shell of Sri is larger than that of Ti. However, the second coordination of both sites remains the same. The water adsorption properties of these substituted zeolites are quantified. Moreover, we explain the higher Lewis acidity of Sn than the Ti site on the basis of the Fukui functions and charge population analysis.

}, issn = {1520-6106}, doi = {10.1021/jp709846s}, author = {Shetty, Sharan and Kulkarni, Bhakti S. and Kanhere, Dilip G. and Goursot, Annick and Pal, Sourav} } @article { ISI:000266989800010, title = {Computational study of electronic structure, thermodynamics and kinetics of hydrogen desorption from Al- and Si-doped alpha-, gamma-, and beta-MgH2}, journal = {Journal of Materials Chemistry}, volume = {19}, number = {25}, year = {2009}, month = {APR}, pages = {4348-4355}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

First principles calculations of pure and Al-and Si-doped alpha-, gamma-, and beta-MgH2 were performed to investigate the influence of Al and Si as impurities and the presence of high pressure phases on the properties of hydrogen sorption of magnesium hydride. The ab initio plane wave pseudopotential method based on density functional theory within the generalized gradient approximation was used in the present study. The total energies of the considered systems were calculated as a function of cell volume to obtain material properties such as bulk modulus K-0, equilibrium cell volume V-0 and minimum energy E-0(V-0). From the density of states (DOS) analysis, it was shown that doping MgH2 with Al and Si caused a reduction in the band gaps of each of the three phases. The diminished band gaps made the Mg-H bond more susceptible to dissociation. The destabilization of the hydrides was reflected in the decreased heats of formation of the doped hydrides, with the following Delta H-f order: Si \< Al and beta \< gamma \< alpha. A 30.5\% reduction in the activation energy barrier E-act for H-2 desorption was calculated for the Al-doped alpha-MgH2(001) surface and a 15.5\% decrease in E-act of the Si-doped gamma-MgH2(001) surface was deduced, while doping with Al and Si increased the activation energy barrier for the beta-MgH2 (001) surface drastically.

}, issn = {0959-9428}, doi = {10.1039/b901115c}, author = {Kelkar, Tuhina and Pal, Sourav} } @article { ISI:000282840600020, title = {Calculation of dipole transition matrix elements and expectation values by vibrational coupled cluster method}, journal = {Journal of Chemical Theory and Computation}, volume = {6}, number = {10}, year = {2010}, month = {OCT}, pages = {3198-3204}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

An effective operator approach based on the coupled cluster method is described and applied to calculate vibrational expectation values and absolute transition matrix elements. Coupled cluster linear response theory (CCLRT) is used to calculate excited states. The convergence pattern of these properties with the rank of the excitation operator is studied. The method is applied to a water molecule. Arponen-type double similarity transformation in extended coupled cluster (ECCM) framework is also used to generate an effective operator, and the convergence pattern of these properties is compared to the normal coupled cluster (NCCM) approach. It is found that the coupled cluster method provides an accurate description of these quantities for low lying vibrational excited states. The ECCM provides a significant improvement for the calculation of the transition matrix elements.

}, issn = {1549-9618}, doi = {10.1021/ct1003669}, author = {Banik, Subrata and Pal, Sourav and Prasad, M. Durga} } @article { ISI:000280708400025, title = {CDASE-A reliable scheme to explain the reactivity sequence between Diels-Alder pairs}, journal = {Physical Chemistry Chemical Physics}, volume = {12}, number = {32}, year = {2010}, month = {JUL}, pages = {9328-9338}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The reliability of the Comprehensive Decomposition Analysis of Stabilization Energy (CDASE) scheme, proposed recently (Phys. Chem. Chem. Phys., 2009, 11, 8306), has been demonstrated in the present study. Reactivity sequence among more than 100 pairs, taking part in Diels-Alder (DA) reaction, is successfully generated by this scheme. The diene series consisted mainly of cis-1,3-butadiene and different substituted butadienes whereas dienophiles are mainly ethylene and its different substitutions. Both the positive energy component (i.e., the energy parameter defined as {\textquoteleft}internal assistance{\textquoteright}) and the negative energy component could generate the expected reactivity trend among the chosen DA pairs, which is also supported by the global electrophilicities of dienes and dienophiles and the corresponding charge-transfer values (Delta N). The numerical values of these components are capable of predicting even the {\textquoteleft}normal electron demand{\textquoteright} (NED) and {\textquoteleft}inverse electron demand{\textquoteright} (IED) nature of the corresponding DA reaction. The method is also capable of reproducing the lower reactivity of acetylene as dienophile when compared to that of ethylene. The reason for the success of CDASE-scheme in explaining intermolecular reactivity sequence is also analysed.

}, issn = {1463-9076}, doi = {10.1039/b925441b}, author = {Saha, Soumen and Roy, Ram Kinkar and Pal, Sourav} } @article { ISI:000274355800017, title = {Comparison of the auxiliary density perturbation theory and the noniterative approximation to the coupled perturbed kohn-sham method: case study of the polarizabilities of disubstituted azoarene molecules}, journal = {Journal of Physical Chemistry A}, volume = {114}, number = {6}, year = {2010}, month = {FEB}, pages = {2357-2364}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

We present a theoretical study of the polarizabilities of free and disubstituted azoarenes employing auxiliary density perturbation theory (ADPT) and the noniterative approximation to the coupled perturbed Kohn-Sham (NIA-CPKS) method. Both methods are noniterative but use different approaches to obtain the perturbed density matrix. NIA-CPKS is different froth the conventional CPKS approach in that the perturbed Kohn-Sham matrix is obtained numerically, thereby yielding a single-step solution to CPKS. ADPT is an alternative approach to the analytical CPKS method in the framework of the auxiliary density functional theory. It is shown that the polarizabilities obtained using these two methods are in good agreement with each other. Comparisons are made for disubstituted azoarenes, which give support to the push-pull mechanism. Both methods reproduce the same trend for polarizabilities because of the substitution pattern of the azoarene moiety. Our results are consistent with the standard organic chemistry {\textquoteleft}{\textquoteleft}activating/deactivating{\textquoteright}{\textquoteright} sequence. We present the polarizabilities of the above molecules calculated with three different exchange-correlation functionals and two different auxiliary function sets. The computational advantages of both methods are also discussed.

}, issn = {1089-5639}, doi = {10.1021/jp909966f}, author = {Shedge, Sapana V. and Carmona-Espindola, Javier and Pal, Sourav and Koster, Andreas M.} } @article { ISI:000310215400007, title = {Conformational modulation of Ant-Pro oligomers using chirality alteration of proline residues}, journal = {Organic \& Biomolecular Chemistry}, volume = {10}, number = {42}, year = {2012}, month = {SEP}, pages = {8426-8433}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Structural modulation of Ant-Pro (anthranilic acid-proline) oligomers has been carried out by chirality alteration of the proline residues. The results suggest that the chirality altered oligomers show well-defined helical conformation featuring nine-membered hydrogen bonding interactions - without compromising conformational rigidity.

}, issn = {1477-0520}, doi = {10.1039/c2ob26132d}, author = {Kale, Sangram S. and Kotmale, Amol S. and Dutta, Achintya Kumar and Pal, Sourav and Rajamohanan, P. R. and Sanjayan, Gangadhar J.} } @article { ISI:000304915100006, title = {Constrained variational approach for energy derivatives in Intermediate hamiltonian fock-space coupled-cluster theory}, journal = {Chemical Physics}, volume = {401}, year = {2012}, month = {JUN}, pages = {45-49}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Fock-space multi-reference coupled cluster theory is an efficient method for electronic structure of nearly degenerate cases. However, it suffers from the intruder state problem for large model space. The intermediate Hamiltonian formulation eliminates intruder state problem and helps in the convergence of equations. In this paper we have implemented intermediate Hamiltonian approach in Fock-space coupled cluster method for the response properties. We test our method for the dipole moments of doublet radicals. We report dipole moments of CN, SF and NS radicals. (C) 2011 Elsevier B. V. All rights reserved.

}, keywords = {Constrained variational approach, Fock-space multi-reference coupled cluster, Intermediate Hamiltonian theory, Response approach}, issn = {0301-0104}, doi = {10.1016/j.chemphys.2011.10.018}, author = {Ghosh, Aryya and Gupta, Jitendra and Pal, Sourav and Vaval, Nayana} } @article { ISI:000325400600023, title = {CAP/EOM-CCSD method for the study of potential curves of resonant states}, journal = {Physical Chemistry Chemical Physics}, volume = {15}, number = {41}, year = {2013}, month = {SEP}, pages = {17915-17921}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The equation-of-motion coupled-cluster (EOM-CC) method along with the complex absorbing potential (CAP) is used for the study of resonance in e(-)-N-2 and e(-)-CO. Resonance position and width are studied as a function of bond length. We report the potential curves (PC) of the resonance states.

}, issn = {1463-9076}, doi = {10.1039/c3cp52552j}, author = {Ghosh, Aryya and Karne, Anagha S. and Pal, Sourav and Vaval, Nayana} } @conference { ISI:000349165104705, title = {Complex absorbing potential based coupled-cluster methods to metastable states}, booktitle = { 248th National Meeting of the American-Chemical-Society (ACS)}, volume = {248}, year = {2014}, note = {248th National Meeting of the American-Chemical-Society (ACS), San Francisco, CA, AUG 10-14, 2014}, month = {AUG}, pages = {Meeting Abstract: 504-COMP}, publisher = {American Chemical Society}, organization = {American Chemical Society}, type = {Meeting Abstract}, address = {1155 16th ST, NW, Washington, DC 20036 USA}, issn = {0065-7727}, author = {Pal, Sourav} } @article { ISI:000344589700016, title = {Complex absorbing potential based equation-of-motion coupled cluster method for the potential energy curve of CO2- anion}, journal = {Journal of Chemical Physics}, volume = {141}, number = {16}, year = {2014}, month = {OCT}, pages = {Article No. 164113}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, abstract = {

The equation-of-motion coupled cluster method employing the complex absorbing potential has been used to investigate the low energy electron scattering by CO2. We have studied the potential energy curve for the (2)Pi(u) resonance states of CO2- upon bending as well as symmetric and asymmetric stretching of the molecule. Specifically, we have stretched the C-O bond length from 1.1 angstrom to 1.5 angstrom and the bending angles are changed between 180 degrees and 132 degrees. Upon bending, the low energy (2)Pi(u) resonance state is split into two components, i.e., (2)A(1), B-2(1) due to the Renner-Teller effect, which behave differently as the molecule is bent. (c) 2014 AIP Publishing LLC.

}, issn = {0021-9606}, doi = {10.1063/1.4899280}, author = {Ghosh, Aryya and Vaval, Nayana and Pal, Sourav and Bartlett, Rodney J.} } @article { ISI:000349902200001, title = {Computational investigation on the catalytic activity of Rh-6 and Rh4Ru2 clusters towards methanol activation}, journal = {Theoretical Chemistry Accounts }, volume = {134}, number = {1}, year = {2014}, month = {DEC}, pages = {1597}, publisher = {SPRINGER}, type = {Article}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Catalysis of molecular activation of small molecules through scission of strong chemical bonds is one of the major challenges faced by chemists. More specifically, activation of the strong C-H and O-H bonds of various alcohols, especially methanol, is one of the various important intermediate steps of key organic reactions. Our present work explores a suitable metal cluster catalyst towards methanol dissociation. In particular, we have examined the effect of ruthenium doping (Rh:Ru = 2:1) on the catalytic activity of Rh-6 cluster towards methanol dissociation. Density functional theory-based calculations illustrate two competitive pathways for methanol dissociation, which are via O-H and C-H bond breaking. Both the pathways are found to be energetically favourable in the presence of bimetallic and mono-metallic clusters. Importantly, energy barrier for O-H bond dissociation reduces considerably in doped cluster as compared to pure Rh-6 cluster and is smaller than the values reported for a number of other small metallic clusters.

}, keywords = {Bimetallic Clusters, Density Functional Theory (DFT), Doping, Methanol Activation, Rhodium Clusters}, issn = {1432-881X}, doi = {10.1007/s00214-014-1597-z}, author = {Ghatak, Kamalika and Sengupta, Turbasu and Krishnamurty, Sailaja and Pal, Sourav} } @article { ISI:000360653900022, title = {Calculation of P,T-odd interaction constant of PbF using Z-vector method in the relativistic coupled-cluster framework}, journal = {Journal of Chemical Physics}, volume = {143}, number = {8}, year = {2015}, month = {AUG}, pages = {084119}, publisher = {AMER INST PHYSICS}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, abstract = {

The effective electric field experienced by the unpaired electron in the ground state of PbF, which is a potential candidate in the search of electron electric dipole moment due to some special characteristics, is calculated using Z-vector method in the coupled cluster single-and double-excitation approximation with four component Dirac spinor. This is an important quantity to set the upper bound limit of the electron electric dipole moment. Further, we have calculated molecular dipole moment and parallel magnetic hyperfine structure constant (A(parallel to)) of Pb-207 in PbF to test the accuracy of the wavefunction obtained in the Z-vector method. The outcome of our calculations clearly suggests that the core electrons have significant contribution to the {\textquoteleft}{\textquoteleft}atom in compound{\textquoteright}{\textquoteright} properties. (C) 2015 AIP Publishing LLC.

}, issn = {0021-9606}, doi = {10.1063/1.4929591}, author = {Sasmal, Sudip and Pathak, Himadri and Nayak, Malaya K. and Vaval, Nayana and Pal, Sourav} } @article { ISI:000356520400003, title = {Computational strategies for understanding the nature of interaction in dioxin imprinted nanoporous trappers}, journal = {Journal of Molecular Recognition}, volume = {28}, number = {7}, year = {2015}, month = {JUL}, pages = {427-437}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

A new computational model capable of understanding the nature of interactions in signature complexes formed between the template(2,3,7,8-tetrachlorodibenzo-p dioxin (TCDD)) and the functional monomers (methacrylic acid (MAA)) using density functional theory (DFT) has been designed. The polymer precursors were optimized for geometries in polymerization media, computing the interaction energies between template molecules and functional monomers of transient pre-polymerized complexes (PPC), and structural and vibrational properties reference to theoretical infrared spectra were computed using DFT of B3LYP/6 311+G(d,p) hybrid functional method. Atom in molecule theory was used to analyze the hydrogen-bonding characteristics of PPC of MAA-TCDD. Considering the theoretical titrations conducted in a virtual solvent box, it was found that the 1:4 molar ratio was required to form the most stable PPC in a given solvent system. The electron density plots indicate strong hydrogen bonding as shown by the 2pz dominant highest occupied molecular orbital (HOMO) character that could be the preferable sites of binding for target molecule, TCDD. Considering HOMO approach, the active adsorption sites in molecularly imprinted polymer was modeled to get insight on molecular recognition property for targeted molecule, TCDD. The proposed computational protocol is simple, accurate, and novel to design the polymer and is useful to predict the properties of polymer systems than the conventional theoretical analysis of template-monomer interactions. Copyright (c) 2015 John Wiley \& Sons, Ltd.

}, keywords = {carcinogenic pollutants, computer simulations, Density Functional Theory (DFT), intermolecular interactions, Molecularly Imprinted Polymers (MIP)}, issn = {0952-3499}, doi = {10.1002/jmr.2459}, author = {Khan, Muntazir S. and Pal, Sourav and Krupadam, Reddithota J.} } @article {43584, title = {Calculation of hyperfine structure constants of small molecules using Z-vector method in the relativistic coupled-cluster framework}, journal = {Journal of Chemical Sciences}, volume = {128}, year = {2016}, month = {OCT}, pages = {1671-1675}, abstract = {The Z-vector method in the relativistic coupled-cluster framework is employed to calculate the parallel and perpendicular components of the magnetic hyperfine structure constant of a few small alkaline earth hydrides (BeH, MgH, and CaH) and fluorides (MgF and CaF). We have compared our Z-vector results with the values calculated by the extended coupled-cluster (ECC) method reported in Phys. Rev. A 91 022512 (2015). All these results are compared with the available experimental values. The Z-vector results are found to be in better agreement with the experimental values than those of the ECC values.}, doi = {10.1007/s12039-016-1174-1}, author = {Sasmal, Sudip and Talukdar, Kaushik and Nayak, Malaya K. and Vaval, Nayana and Pal, Sourav} } @article {43596, title = {Contriving a catalytically active structure from an inert conformation: a density functionalinvestigation of Al, Hf, and Ge doping of Au-20 tetrahedral clusters}, journal = {Journal of Physical Chemistry C}, volume = {120}, year = {2016}, month = {SEP}, pages = {19636-19641}, abstract = {

The transformation of an inert structure into a catalytically active conformation has immense potential from a structural engineering point of view. In the present work, we explored methods of achieving such a transformation through a density-functional-based study. Au-20 is known be one of the most stable and catalytically inert gold clusters, with a well-known tetrahedral structure. We demonstrate the transformation of the inert Au-20 conformation into a highly active catalytic cluster through selective doping with Hf and Ge atoms. Depending on the dopant, the inert tetrahedral Au-20 cluster evolves into either an endohedral or a hollow-cage-like conformation. The structural changes are manifested in the catalytic properties as well, with the result that the transformed doped cages exhibit extremely low activation barriers for the environmentally important CO oxidation reaction as compared to reported inert Au-20 cluster. The activation barriers for CO oxidation are particularly low (\<0.12 eV) when germanium is directly involved in the CO oxidation. Thus, the current work highlights the importance of engineering structural properties of metal nanoclusters with the help of heteroatom dopants for future applications in efficient catalysis.

}, doi = {10.1021/acs.jpcc.6b04305}, author = {Manzoor, Dar and Krishnamurty, Sailaja and Pal, Sourav} } @article {44640, title = {Correlation trends in the magnetic hyperfine structure of atoms: a relativistic coupled-cluster case study}, journal = {Physical Review A}, volume = {98}, year = {2018}, month = {AUG}, type = {Article}, abstract = {

The role of electron correlation in the hyperfine structure of alkali metals and alkaline earth metal monopositive ions in their ground electronic configuration is investigated using the Z-vector method in a relativistic coupled-cluster regime within the singles and doubles approximation. The systematic effects of core-correlating functions, polarization of core electrons, and high-lying virtual functions on core electrons correlation are studied. The study reveals that the core-correlating function plays a significant role in core polarization and thus is very important for precise calculation of the wave function near the nuclear region. The inner-core electrons (1s-2p) require very high virtual energy functions for proper correlation. Therefore, the all-electron correlation treatment and the inclusion of higher-energy virtual functions are the key factors for precise calculation of the hyperfine structure constant of atoms. Our calculated values are in excellent agreement with the available experimental values, which also implies that the wave function produced by the Z-vector method is accurate enough for further calculation of the parity- and time-reversal symmetry-violating properties in atoms and molecules.

}, issn = {2469-9926}, doi = {10.1103/PhysRevA.98.022507}, author = {Talukdar, Kaushik and Sasmal, Sudip and Nayak, Malaya K. and Vaval, Nayana and Pal, Sourav} }