On HPHT Hydraulic Cubic Press , the multi-seed method significantly enhances the synthesis efficiency of gem-grade diamonds through the following aspects:
Effective Utilization of Cavity Space, Solving the Problem of Low Resource Utilization Rate:
    With the scaling up of high-pressure synthesis equipment, high-temperature and high-pressure cavities also expand. However, traditional methods for synthesizing gem-grade diamonds usually place only one diamond seed in a synthesis cavity, leading to severe waste of cavity resources in larger synthesis cavities.
    The core idea of the multi-seed method is to simultaneously place multiple diamond seeds (e.g., 3-5 seeds) in a single synthesis cavity, achieving synchronous crystal growth and ensuring that the crystals do not touch each other after growing larger, thereby fully utilizing the space of the reaction cavity.
    This method effectively addresses the critical issue of low utilization rates of high-temperature and high-pressure resources in large-scale presses.
Significant Increase in Overall Growth Rate, Boosting Output per Experiment:
    The multi-seed method increases the area for receiving diffused carbon, thereby enhancing carbon acceptance capacity, which requires sufficient carbon to support the simultaneous growth of multiple seeds.
    Although the growth rate of a single crystal is approximately 2.0—2.5 mg/h, which is consistent with the required rate for growing high-quality Ib type diamond single crystals, the total growth rate of all crystals combined is significantly improved under the multi-seed method.
    For example, in four-seed method experiments, the total growth rate of all crystals can reach 6.45—7.1 mg/h. This increase in overall growth rate leads to a marked improvement in the synthesis efficiency of a single experiment.
Achieving Batch Production with Consistent Morphology and Quality:
    Through the multi-seed method, multiple high-quality Ib type gem-grade diamond single crystals with consistent morphology and quality can be synthesized in a single experiment, typically presenting a light yellow color.
    This capability makes it possible to mass-produce high-quality crystals in larger cavities and enable their industrialization.
Providing Important Basis for Commercial Production:
    Research into the multi-seed method not only effectively improves the efficiency of single-crystal diamond synthesis in a single cycle but also provides an important theoretical and experimental basis for the commercial production of gem-grade single-crystal diamonds.
To support crystal growth under the multi-seed method, corresponding parameter adjustments are required on domestic six-sided presses:
Appropriately increase synthesis pressure: Due to the higher demands on the diamond stability range within the cavity introduced by multiple seeds, the synthesis pressure needs to be appropriately increased to, for example, 5.4—5.7 GPa (compared to 5.5 GPa for the single-seed method). This widens the diamond synthesis range to counteract the higher requirements brought by the introduction of multiple seeds.
Employ a larger temperature gradient: To satisfy the demand of multiple seeds for sufficient carbon, the cavity assembly design needs to incorporate a larger temperature gradient to create a sufficiently large carbon concentration gradient.