Performance of Localized-Orbital Coupled-Cluster Approaches for the Conformational Energies of Longer n ‑Alkane Chains

• Main Authors: Golokesh Santra (6824864), Jan M.L. Martin (537232)
• Format: Other Non-Article Part of Journal/Newspaper
• Language: unknown
• Published: 2022
• Subjects: Biophysics; Biochemistry; Physiology; Evolutionary Biology; Cancer; Space Science; Biological Sciences not elsewhere classified; Chemical Sciences not elsewhere classified; s66x8 noncovalent interactions; related truncation errors; may upend orderings; given accuracy threshold; gets slightly better; best pick among; >‑ alkane chains; )]- based post; based methods tested; revised reference data; less accurate methods; vtight – tight; statistically similar accuracy; large alkanes [<; explicitly correlated dlpno; e .; ccsd; f12 ]/ aug; revised aconfl set; f12 *)- mp2; cutpno </ sub; accurate methods; reference datasets; )/ aug; f12 extrapolation; basis set; aconfl set; aconf12 set; ultimately finding; perturbative triples; n </; n -</; improves things; gradually tightening; error statistics; dodecane conformers; cutoffs improves; conventional ccsd; conformer energies; conformational energies; composite scheme; canonical mp2; Orca
• Online Access: https://doi.org/10.1021/acs.jpca.2c06407.s001

We report an update and enhancement of the ACONFL (conformer energies of large alkanes [ J. Phys. Chem. A 2022, 126 , 3521–3535]) dataset. For the ACONF12 ( n -dodecane) subset, we report basis set limit canonical coupled-cluster with singles, doubles, and perturbative triples [i.e., CCSD(T)] reference data obtained from the MP2-F12/cc-pV{T,Q}Z-F12 extrapolation, [CCSD(F12*)-MP2-F12]/aug-cc-pVTZ-F12, and a (T) correction from conventional CCSD(T)/aug-cc-pV{D,T}Z calculations. Then, we explored the performance of a variety of single and composite localized-orbital CCSD(T) approximations, ultimately finding an affordable localized natural orbital CCSD(T) [LNO-CCSD(T)]-based post-MP2 correction that agrees to 0.006 kcal/mol mean absolute deviation with the revised canonical reference data. In tandem with canonical MP2-F12 complete basis set extrapolation, this was then used to re-evaluate the ACONF16 and ACONF20 subsets for n- hexadecane and n- icosane, respectively. Combining those with the revised canonical reference data for the dodecane conformers (i.e., ACONF12 subset), a revised ACONFL set was obtained. It was then used to assess the performance of different localized-orbital coupled-cluster approaches, such as pair natural orbital localized CCSD(T) [PNO-LCCSD(T)] as implemented in MOLPRO, DLPNO-CCSD(T 0 ) and DLPNO-CCSD(T 1 ) as implemented in ORCA, and LNO-CCSD(T) as implemented in MRCC, at their respective “Normal”, “Tight”, “vTight”, and “vvTight” accuracy settings. For a given accuracy threshold and basis set, DLPNO-CCSD(T 1 ) and DLPNO-CCSD(T 0 ) perform comparably. With “VeryTightPNO” cutoffs, explicitly correlated DLPNO-CCSD(T 1 )-F12/VDZ-F12 is the best pick among all the DLPNO-based methods tested. To isolate basis set incompleteness from localized-orbital-related truncation errors (domain, LNOs), we have also compared the localized coupled-cluster approaches with canonical DF-CCSD(T)/aug-cc-pVTZ for the ACONF12 set. We found that gradually tightening the cutoffs improves the performance of ...