Several single reference (SR-CC) coupled cluster methods are shown to work for traditionally multi-reference (MR) problems such as bond breaking subject to restricted Hartree-Fock (RHF) references. The correlated methods can successfully describe any MR problem with enough higher order clusters: singles and doubles (CCSD), singles, doubles and triples (CCSDT), singles, doubles, triples, and quadruples (CCSDTQ), etc. However, due to the steep increase in the computational cost, it is not practical to do larger systems or to use large basis sets without active space partitioning. In this study, the orbital space is partitioned into an active space subject to an unambiguous statistical criteria to span the MR behavior which defines an extended space to let the active space relax. The rest is considered the external space. The extended space is treated with CCSDT and the external space with CCSD. An automated scheme for determining the extended space is presented and evaluated. We build upon the tailored-CC scheme of Hino et al. and address its main shortcoming of neglecting the coupling between the active space and the rest of the orbital space which results in loss of accuracy as well as a pronounced nonparallelism error (NPE). The automated scheme makes it unnecessary for the user to judge whether a chosen active space is sufficient to correctly solve the problem. We illustrate this method for the hydrogen fluoride and fluorine molecule ground state dissociation potentials using the extended space partitioning methods. Experimental accuracy for the dissociation energy is achieved at a small fraction of the cost of doing a full CCSDT calculation. This approach is easily amendable to higher order clusters which are required for double and triple bond breaking and other strongly multi-reference systems.

A quantum chemical study of spectral shifts by single molecule solvation of phenol, α-naphthol, and β-naphthol is presented. The methods employed include the equation-of-motion coupled cluster, the similarity transformed equation-of-motion coupled cluster, single excitation configuration-interaction, and time-dependent density functional theory. Based on the calculations, there is no evidence that there is significant charge-transfer between the solute and the solvent. Instead, it appears that the observed solvation redshift is due to the nature of the excited state on the solute molecule.

Aims: To investigate the potential of a signal processed by smartphone-case based on single lead electrocardiogram (ECG) for left ventricular diastolic dysfunction (LVDD) determination as a screening method. Methods and Results: We included 446 subjects for sample learning and 259 patients for sample test aged 39 to 74 years for testing with 2D-echocardiography, tissue Doppler imaging and ECG using a smartphone-case based single lead ECG monitor for the assessment of LVDD. Spectral analysis of ECG signals (spECG) has been used in combination with advanced signal processing and artificial intelligence methods. Wavelengths slope, time intervals between waves, amplitudes at different points of the ECG complexes, energy of the ECG signal and asymmetry indices were analyzed. The QTc interval indicated significant diastolic dysfunction with a sensitivity of 78% and a specificity of 65%, a Tpeak parameter >590 ms with 63% and 58%, a T value off >695 ms with 63% and 74%, and QRSfi > 674 ms with 74% and 57%, respectively. A combination of the threshold values from all 4 parameters increased sensitivity to 86% and specificity to 70%, respectively (OR 11.7 [2.7-50.9], P < .001). Algorithm approbation have shown: Sensitivity—95.6%, Specificity—97.7%, Diagnostic accuracy—96.5% and Repeatability—98.8%. Conclusion: Our results indicate a great potential of a smartphone-case based on single lead ECG as novel screening tool for LVDD if spECG is used in combination with advanced signal processing and machine learning technologies.

A procedure is presented to obtain accurate absorption cross-sections for dissociative excited states. The focus is the ability to approximate many vibrational degrees of freedom while maintaining a minimal computational time. The vibrational Hamiltonian for bound and unbound surfaces is solved within a discrete variable representation (DVR) framework. Properties and energies of excited states are computed using electron correlated singles and doubles equation-of-motion (EOM-CCSD) and similarity transformed equation-of-motion (STEOM-CCSD) methods as implemented in ACESII. The novelty of this procedure is that it is designed to work for medium-sized molecules (size limited by the choice of electronic structure method, not vibrational degrees of freedom) with one or more photodissociation pathways. The theoretical absorption cross-section of NaOH is presented as a small-scale example.