657, a method for estimating tetrahedral bond angles

A DFT-Based Quantitative and Geometric Analysis of the Effect of Pressure on Boron Arsenate

“…In other words, the central atom within the tetrahedron bisects a line which is the perpendicular bisector of the two Set 1 edges. Another interesting phenomenon that should be noted is that for each tetrahedron in our system, the sum of the six O-As-O or O-B-O bond angles sum up to approximately 657° (i.e., ≈6 × 109.47°), which as noted by McNelis and Blandino [ 60 ] from their examination of many tetrahedral systems, seems to be a value which applies to practically all tetrahedral molecular units.…”

“…Verified that the rule proposed around two decades ago by McNelis and Blandino [ 60 ] concerning tetrahedral bond angles is not just applicable at ambient pressures but also at the extreme pressures such as the ones applied here.…”

“…In fact, as shown in Table 2 , the predition holds perfectly (100% agreement) for the data obtained experimentally, i.e., c eqn the value of c predicted by Equation (6) is exacly identical to c act , the value of c actually measured and the values of a and b as computed through Equation (19) are equal to those actually measured directly in the experiment and simuations. Moreover, the rule proposed by McNelis and Blandino [ 60 ] was also found to be fully applicable to the simulated crystal structure, as shown in Table 1 .…”

“…Before concluding it is important to point out some of the main strengths and limitations of the present study. An important strength is its novelty: This work has, for the first time: Reported the predicted compressibility of BAsO 4 over a much wider range of pressures compared to what was reported before, including very extreme pressures; Identified three rather distinct regions with different compressibility characteristics in c direction (one NLC region, two PLC regions); Analysed the structure of BAsO 4 from a purely geometric perspective, in the process revealing various interesting features such as the tetrahedra are tetragonal disphenoids, a shape which is retained over a very wide range of pressure; Developed a new approach for examining compressibility by presenting a mathematical parametric model based on geometric and mechanistic considerations which permit the quantification of the relative contributions to the overall compressibility, both positive and negative, thus be able to unlock in a quantifiable manner what gives rise to NLC or otherwise; Proved in a quantitative manner than the proposed ‘demi wine-rack’ mechanisms involving tetrahedra deformations is indeed the mechanisms which leads to NLC, rather than the more conspicuous tetrahedra rotations; Verified that the rule proposed around two decades ago by McNelis and Blandino [ 60 ] concerning tetrahedral bond angles is not just applicable at ambient pressures but also at the extreme pressures such as the ones applied here. …”

Complexes of 1,3-Diisobutyl Thiourea with Copper(I), Zinc(II) and Mercury(II): Their Antioxidant and Antibacterial Evaluation

“…The ligand is attached through the S atom, as normally expected for this class of compounds. The angles S1-Cu1-S1 and S1-Cu1-I1 are 100.32(2) and 117.55 (16), respectively, with the sum of all six angles amounting to 653.6 • , which supports distorted tetrahedral geometry around the metal ion [49]. These features are within the expected limit and are very close to structurally analogous complexes [50,51].…”