From owner-chemistry $#at#$ ccl.net Wed Dec 25 12:12:00 2019 From: "Thomas Manz thomasamanz()gmail.com" To: CCL Subject: CCL: crystal orbital Hamilton populations Message-Id: <-53915-191225115839-17575-NkU6I28Uv9eIrIXrvbsPgA%a%server.ccl.net> X-Original-From: Thomas Manz Content-Type: multipart/alternative; boundary="000000000000a158eb059a8a2b40" Date: Wed, 25 Dec 2019 09:58:22 -0700 MIME-Version: 1.0 Sent to CCL by: Thomas Manz [thomasamanz..gmail.com] --000000000000a158eb059a8a2b40 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Dear colleagues, Recently, Taoyi Chen and I published a journal article studying the bond orders of 288 diatomic molecules and ions: T. Chen and T. A. Manz, "Bond orders of the diatomic molecules," RSC Advances, 9 (2019) 17072-17092 http://doi.org/10.1039/C9RA00974D (open access). While doing the literature review for that article, I was surprised to find there had been no prior studies of quantum-mechanically computed bond orders across a large set of diatomic molecules. Several prior studies did look at quantum-mechanically computed bond orders for a small set of diatomics, although the largest set appears to be my own prior study that included quantum-mechanically computed bond orders for 26 diatomics as part of a large study introducing a comprehensive method to compute bond orders: T. A. Manz, =E2=80=9CIntroducing DDEC6 atomic population analysis: = part 3. Comprehensive method to compute bond orders,=E2=80=9D RSC Advances, 7 (2017= ) 45552-45581 http://doi.org/10.1039/c7ra07400j (open access). Now, I'm trying to better understand the bonding, non-bonding, and anti-bonding contributions of individual occupied Kohn-Sham orbitals in period 2 homodiatomics and other molecules. Due to the s-p mixing in some of the period 2 homodiatomics, this problem is not as straightforward as often assumed. For example, the bond order of Be2 is around 0.65 which occurs because s-p mixing makes the 1 sigma u valence orbital only slightly anti-bonding. (Here, the core orbitals are not included in the numbering scheme, so 1 sigma g is the lowest energy molecular valence orbital.) My question is to what extent approaches like Crystal Orbital Hamilton Populations (COHP or projected-COHP) or Crystal Orbital Overlap Populations (COOP) have been used to study diatomic molecules? Specifically, not just the integrated total COHP/pCOHP or COOP value, but the value of these descriptors plotted versus the orbital/band energy? These could be calculations on an isolated molecule using a localized basis set or periodic calculations using a single molecule placed in the center of a large periodic unit cell. In particular, has any prior literature investigated the claimed correlation between the sign of COHP/pCOHP and the bonding vs. anti-bonding orbital characteristics for molecules whose bonding, non-bonding, or anti-bonding contributions of individual orbitals/bands are independently assessed? For example, have any published studies demonstrated that the COHP/pCOHP or COOP approaches can accurately reproduce the bonding, non-bonding, and anti-bonding characteristics of individual orbitals/bands in period 2 homodiatomics (Li2, Be2, B2, C2, N2, O2, F2, and Ne2) or other small molecules? An even more pointed question: Does the COHP approach predict the 1 sigma u valence orbital in N2 is bonding, anti-bonding, or approximately non-bonding? How about the 2 sigma g valence orbital in N2? Can anyone point me to COHP/pCOHP or COOP studies for isolated molecules that have tried to assess the reliability of the sign change of these descriptors for identifying orbitals/bands as bonding, anti-bonding, or non-bonding? Sincerest thanks, Tom Manz --000000000000a158eb059a8a2b40 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Dear colleagues,

Recently, Taoyi Chen and I publish= ed a journal article studying the bond orders of 288 diatomic molecules and= ions: T. Chen and T. A. Manz, "Bond orders of the diatomic molecules,= " RSC Advances, 9 (2019) 17072-17092 http://doi.org/10.1039/C9RA00974D (open access).

Wh= ile doing the literature review for that article, I was surprised to find t= here had been no prior studies of quantum-mechanically computed bond orders= across a large set of diatomic molecules. Several prior studies did look a= t quantum-mechanically computed bond orders for a small set of diatomics, a= lthough the largest set appears to be my own prior study that included quan= tum-mechanically computed bond orders for 26 diatomics as part of a large s= tudy introducing a comprehensive method to compute bond orders:=C2=A0T. A. = Manz, =E2=80=9CIntroducing DDEC6 atomic population analysis: part 3. Compre= hensive method to compute bond orders,=E2=80=9D RSC Advances, 7 (2017) 4555= 2-45581 http://doi.org/10.103= 9/c7ra07400j (open access).

Now, I'm trying to better under= stand the bonding, non-bonding, and anti-bonding contributions of individua= l occupied Kohn-Sham orbitals in period 2 homodiatomics and other molecules= . Due to the s-p mixing in some of the period 2 homodiatomics, this problem= is not as straightforward as often assumed. For example, the bond order of= Be2 is around 0.65 which occurs because s-p mixing makes the 1 sigma u val= ence orbital only slightly anti-bonding. (Here, the core orbitals are not i= ncluded in the numbering scheme, so 1 sigma g is the lowest energy molecula= r valence orbital.)

My question is to what extent = approaches like Crystal Orbital Hamilton Populations (COHP or projected-COH= P) or Crystal Orbital Overlap Populations (COOP) have been used to study di= atomic molecules? Specifically, not just the integrated total COHP/pCOHP or= COOP value, but the value of these descriptors plotted versus the orbital/= band energy? These could be calculations on an isolated molecule using a lo= calized basis set or periodic calculations using a single molecule placed i= n the center of a large periodic unit cell. In particular, has any prior li= terature investigated the claimed correlation between the sign of COHP/pCOH= P and the bonding vs. anti-bonding orbital characteristics for molecules wh= ose bonding, non-bonding, or anti-bonding contributions of individual orbit= als/bands are independently assessed? For example, have any published studi= es demonstrated that the COHP/pCOHP or COOP approaches can accurately repro= duce the bonding, non-bonding, and anti-bonding characteristics of individu= al orbitals/bands in period 2 homodiatomics (Li2, Be2, B2, C2, N2, O2, F2, = and Ne2) or other small molecules? An even more pointed question: Does the = COHP approach predict the 1 sigma u valence orbital in N2 is bonding, anti-= bonding, or approximately non-bonding? How about the 2 sigma g valence orbi= tal in N2?

Can anyone point me to COHP/pCOHP or CO= OP studies for isolated molecules that have tried to assess the reliability= of the sign change of these descriptors for identifying orbitals/bands as = bonding, anti-bonding, or non-bonding?

Sincerest thanks,

Tom = Manz
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