From owner-chemistry _-at-_)ccl.net Wed Dec 25 16:35:00 2019 From: "David Mannock dmannock(a)yahoo.com" To: CCL Subject: CCL: crystal orbital Hamilton populations Message-Id: <-53916-191225162543-28058-9T0nL3cROnL39mbFVvkYug-,-server.ccl.net> X-Original-From: David Mannock Content-Type: multipart/alternative; boundary="----=_Part_3581322_819184140.1577309136012" Date: Wed, 25 Dec 2019 21:25:36 +0000 (UTC) MIME-Version: 1.0 Sent to CCL by: David Mannock [dmannock__yahoo.com] ------=_Part_3581322_819184140.1577309136012 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Tom, A very interesting & truly refreshing message in my inbox on Christmas day!= It was well written with excellent explanations for those of us who are ge= neralists in CC. I read through it with genuine interest & came away with s= ome understanding of your purpose. Please keep the list updated of your fin= dings. I will mention one point that I have experienced in studying steroids which= is that there was considerable work in the literature pre-1980 sans PC. I = was told by a PDF that he did not look at any literature pre-1995! Sadly, t= his meant that he missed crucial papers on point that were not yet digitize= d! A strange attitude that results in each generation of young scientists r= e-inventing the wheel which is occasionally round! Thanks for the message &= Seasons Greetings to you and your family. David Mannock On Wednesday, December 25, 2019, 10:33:54 a.m. MST, Thomas Manz thomasa= manz()gmail.com wrote: =20 =20 Dear colleagues, Recently, Taoyi Chen and I published a journal article studying the bond or= ders of 288 diatomic molecules and ions: T. Chen and T. A. Manz, "Bond orde= rs of the diatomic molecules," RSC Advances, 9 (2019) 17072-17092 http://do= i.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 orde= rs 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 qu= antum-mechanically computed bond orders for 26 diatomics as part of a large= study introducing a comprehensive method to compute bond orders:=C2=A0T. A= . Manz, =E2=80=9CIntroducing DDEC6 atomic population analysis: part 3. Comp= rehensive method to compute bond orders,=E2=80=9D RSC Advances, 7 (2017) 45= 552-45581 http://doi.org/10.1039/c7ra07400j (open access). Now, I'm trying to better understand the bonding, non-bonding, and anti-bon= ding contributions of individual occupied Kohn-Sham orbitals in period 2 ho= modiatomics and other molecules. Due to the s-p mixing in some of the perio= d 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. (He= re, 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 Popu= lations (COHP or projected-COHP) or Crystal Orbital Overlap Populations (CO= OP) have been used to study diatomic molecules? Specifically, not just the = integrated total COHP/pCOHP or COOP value, but the value of these descripto= rs plotted versus the orbital/band energy? These could be calculations on a= n isolated molecule using a localized basis set or periodic calculations us= ing a single molecule placed in the center of a large periodic unit cell. I= n particular, has any prior literature investigated the claimed correlation= between the sign of COHP/pCOHP and the bonding vs. anti-bonding orbital ch= aracteristics for molecules whose bonding, non-bonding, or anti-bonding con= tributions of individual orbitals/bands are independently assessed? For exa= mple, have any published studies demonstrated that the COHP/pCOHP or COOP a= pproaches can accurately reproduce the bonding, non-bonding, and anti-bondi= ng characteristics of individual orbitals/bands in period 2 homodiatomics (= Li2, Be2, B2, C2, N2, O2, F2, and Ne2) or other small molecules? An even mo= re pointed question: Does the COHP approach predict the 1 sigma u valence o= rbital in N2 is bonding, anti-bonding, or approximately non-bonding? How ab= out the 2 sigma g valence orbital in N2? Can anyone point me to COHP/pCOHP or COOP studies for isolated molecules th= at have tried to assess the reliability of the sign change of these descrip= tors for identifying orbitals/bands as bonding, anti-bonding, or non-bondin= g? Sincerest thanks, Tom Manz =20 ------=_Part_3581322_819184140.1577309136012 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
<= /div>
Tom,

A ver= y interesting & truly refreshing message in my inbox on Christmas day! = It was well written with excellent explanations for those of us who are gen= eralists in CC. I read through it with genuine interest & came away wit= h some understanding of your purpose. Please keep the list updated of your = findings.

I will mention one point that I have experience= d in studying steroids which is that there was considerable work in the lit= erature pre-1980 sans PC. I was told by a PDF that he did not look at any l= iterature pre-1995! Sadly, this meant that he missed crucial papers on poin= t that were not yet digitized! A strange attitude that results in each gene= ration of young scientists re-inventing the wheel which is occasionally rou= nd! Thanks for the message & Seasons Greetings to you and your family.<= /div>

David Mannock

=20
=20
On Wednesday, December 25, 2019, 10:33:54 a.m. MST, Tho= mas Manz thomasamanz()gmail.com <owner-chemistry(a)ccl.net> wrote:


Dear collea= gues,

Recently, Taoyi Chen and I published a journal article studyin= g the bond orders of 288 diatomic molecules and ions: T. Chen and T. A. Man= z, "Bond orders of the diatomic molecules," RSC Advances, 9 (2019) 17072-17= 092 http://doi.org/10.1039/C9RA00974D (open access).

While= doing the literature review for that article, I was surprised to find ther= e had been no prior studies of quantum-mechanically computed bond orders ac= ross a large set of diatomic molecules. Several prior studies did look at q= uantum-mechanically computed bond orders for a small set of diatomics, alth= ough 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 stud= y introducing a comprehensive method to compute bond orders: T. A. Man= z, =E2=80=9CIntroducing DDEC6 atomic population analysis: part 3. Comprehen= sive method to compute bond orders,=E2=80=9D RSC Advances, 7 (2017) 45552-4= 5581 http://doi.org/10.1039/c7ra07400j (open access).

Now, I'm trying to better understan= d the bonding, non-bonding, and anti-bonding contributions of individual oc= cupied Kohn-Sham orbitals in period 2 homodiatomics and other molecules. Du= e 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 inclu= ded in the numbering scheme, so 1 sigma g is the lowest energy molecular va= lence orbital.)

My question is to what extent appr= oaches like Crystal Orbital Hamilton Populations (COHP or projected-COHP) o= r Crystal Orbital Overlap Populations (COOP) have been used to study diatom= ic molecules? Specifically, not just the integrated total COHP/pCOHP or COO= P value, but the value of these descriptors plotted versus the orbital/band= energy? These could be calculations on an isolated molecule using a locali= zed basis set or periodic calculations using a single molecule placed in th= e center of a large periodic unit cell. In particular, has any prior litera= ture investigated the claimed correlation between the sign of COHP/pCOHP an= d 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 d= emonstrated that the COHP/pCOHP or COOP approaches can accurately reproduce= the bonding, non-bonding, and anti-bonding characteristics of individual o= rbitals/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-bond= ing, or approximately non-bonding? How about the 2 sigma g valence orbital = in N2?

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

Sincerest thanks,

Tom Manz=
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