Tsz sian Chwee

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We demonstrate that valence excited states in large molecules can be treated using local multireference singles and doubles configuration interaction (LMRSDCI). The interior eigenvalues corresponding to the excited states of interest are transformed and shifted to the extrema of the spectrum by way of oblique projections and a matrix shift within a modified(More)
The adsorption energies and changes in surface work functions for benzene on unreconstructed Cu(111), Ag (111), and Au (111) at low coverages have been studied within the framework of dispersion corrected Kohn-Sham density functional theory. Corrections to account for long range dispersive effects between the adsorbate and metal substrate were incorporated(More)
A local multireference singles and doubles configuration interaction method in which Cholesky vectors are used in place of conventional two-electron integrals has been developed (CD-LMRSDCI). To reduce the overall cost associated with our linear scaling LMRSDCI method presented earlier [T. S. Chwee et al., J. Chem. Phys. 128, 224106 (2008)], we adopt a(More)
A linear scaling multireference singles and doubles configuration interaction (MRSDCI) method has been developed. By using localized bases to span the occupied and virtual subspace, local truncation schemes can be applied in tandem with integral screening to reduce the various bottlenecks in a MRSDCI calculation. Among these, the evaluation of electron(More)
Topological insulators (TIs) represent an exciting new class of materials with potential applications in spintronics and quantum computing. In this work, we present a theoretical study on a new family of two dimensional (2D) nanomaterials based on the coordination of shape persistent organic ligands (SPOLs) to heavy transition metal ions such as Pd(2+) and(More)
Thin-layer chromatography (TLC) coupled with surface enhanced Raman spectroscopy (SERS) has been widely used for the study of various complex systems, especially for the detection of adulterants in botanical dietary supplements (BDS). However, this method is not sufficient to distinguish structurally similar adulterants in BDS since the analogs have highly(More)
The overall rate coefficients of the reactions of CSe2, SCSe, and OCSe with O(3P) atom have been determined to be k(CSe2) = (1.4 +/- 0.2) x 10(-10) cm3 molecule(-1) s(-1), k(SCSe) = (2.8 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1), and k(OCSe) = (2.4 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1) at 301-303 K using Fourier transform infrared (FTIR) absorption(More)
Fluorescence lifetimes were evaluated using TD-DFT under different approximations for the emitting molecule and various exchange-correlation functionals, such as B3LYP, BMK, CAM-B3LYP, LC-BLYP, M06, M06-2X, M11, PBE0, ωB97, ωB97X, LC-BLYP*, and ωB97X* where the range-separation parameters in the last two functionals were tuned in a non-empirical fashion.(More)
We have carried out first principles electronic structure calculations on the ground and excited valence states of syn and anti bimanes. While syn bimanes fluoresce strongly after photoexcitation to the first excited singlet state (S1) and are commonly used as fluorophores in biological labeling studies, anti bimanes largely phosphoresce at low(More)
We have studied the performance of dual basis (DB) sets for the evaluation of molecular properties via second order Møller-Plesset perturbation theory (MP2). In addition to savings derived from using a trimmed basis set for the underlying Hartree-Fock (HF) calculation, we pursued a systematic truncation of the virtual subspace for further reductions in(More)